Callstack

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Details

Founded:
2016
Hourly Rates:
Undisclosed
Employees:
50 - 249
Ratings:
4.5 9 Reviews

Industries Served

Environmental Services Construction Mining & Metals Sports & Fitness Real Estate Aerospace & Defense Nonprofit & NGO Government & Public Sector Media & Entertainment

Where We Specialize

33% Mobile App Development
Mobile App Development 33%
AI Development 29%
Testing Services 13%
Implementation Services 10%
Bot Development 9%
Regression 6%

Industry Expertise

Automotive65% Manufacturing35%

Typical Project Size

44% Midmarket Business
35% Enterprise
21% Small Business

About

Since 2016, Callstack has operated as a technology services provider. Their core services include Mobile App Development. With 50 - 249 people on staff, Callstack can take on projects of varying size. Callstack holds a 4.8-star rating across 2 client reviews. The team is based in Wrocław, Poland. Overall, Callstack is one of the options worth shortlisting for a technology project.

Callstack Reviews

4.5 9 Reviews
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Solid IT Consulting Work With Clear Communication Throughout

Wei Jie Goh / IT Director | Aug 24, 2026

Honestly, this was one of the smoothest projects we have run with an outside team. We dealt with the same core team throughout, so we did not have to keep re-explaining things. When we changed our minds on a couple of features halfway through, they handled it without fuss and were clear about the impact on cost and timeline. Even with the time zone difference, responses usually came the same day and we never felt left in the dark.

Feedback from our customers has been very positive so far.

I would recommend Callstack to anyone looking for a dependable IT Consulting partner.

Project summary

We hired Callstack to help us choose and plan the rollout of a new core system. Their team handled planning, development and QA, with our product owner signing off each milestone. Overall it was a 7-month engagement.

  • Overall Rating 4.5
  • Quality 4.0
  • Schedule 5.0
  • Project Cost 5.0
  • Willing To Refer 5.0
Project Type:
IT Consulting
Project Cost:
$500,000+
Project Duration:
Dec 2025 - Jul 2026
Business Type:
Environmental Services
Location:
Singapore

Questions & Answers

Please describe your company, your role, and the industry you operate in.
We're a mid-sized Environmental Services company based in Singapore. I'm the IT Director and I oversaw the project from start to finish.
What specific problem or business challenge led you to hire this company?
Our team was spending too much time on manual work. The goal was to help us choose and plan the rollout of a new core system so they could focus on customers.
What services did the company provide for your project?
IT Consulting, plus QA and some consulting on how to structure the project.
Why did you choose this company over other providers you considered?
A colleague recommended them, and our first calls confirmed they understood what we needed.
How clearly did the company understand your requirements and business goals?
Better than we expected. They pointed out a few things we had not thought about.
How was your overall experience with their communication and project management?
Communication was good overall and improved further once we settled into a routine.
Did the company deliver the project on time and within your expected budget?
Mostly. One milestone slipped by about a week, but the final delivery was on schedule and the budget held.
What tangible results or business impact have you seen since the project was completed?
Our team saves several hours a week, and we have had very few issues since launch.
What did you like most about working with this company?
The consistency. Same team, same standard, from the first week to the last.
Would you recommend this company to others, and would you work with them again?
Yes. They are a reliable IT Consulting partner.

Delivered on time and stayed involved after launch

Saud Al Qahtani / Co-Founder & CTO | Aug 24, 2026

I would rate this engagement highly on almost every front. We dealt with the same core team throughout, so we did not have to keep re-explaining things. The developers were knowledgeable and made a few suggestions that ended up saving us time and money.

We launched on schedule and have not had any major issues since.

We are already discussing the next phase with them.

Project summary

Our company worked with Callstack to automate document data extraction that our team was doing by hand. They worked alongside our in-house team, which mostly handled business requirements and testing. Overall it was a 4-month engagement.

  • Overall Rating 4.5
  • Quality 4.5
  • Schedule 4.5
  • Project Cost 4.0
  • Willing To Refer 5.0
Project Type:
AI & Machine Learning
Project Cost:
Less than $10,000
Project Duration:
Feb 2026 - Jun 2026
Business Type:
Construction
Location:
Jeddah, Saudi Arabia

Questions & Answers

Please describe your company, your role, and the industry you operate in.
Lakeshore Projects Co is a Construction business in Jeddah, Saudi Arabia. As Co-Founder & CTO, I was responsible for this project on our side and the main contact for Callstack.
What specific problem or business challenge led you to hire this company?
Our team was spending too much time on manual work. The goal was to automate document data extraction that our team was doing by hand so they could focus on customers.
What services did the company provide for your project?
AI & Machine Learning, plus QA and some consulting on how to structure the project.
Why did you choose this company over other providers you considered?
They had relevant experience in Construction and their proposal was the clearest of the ones we received.
How clearly did the company understand your requirements and business goals?
Well. There were a couple of points we had to clarify early on, but after that they were spot on.
How was your overall experience with their communication and project management?
Organised and transparent. Their project manager kept the project on track and flagged risks early.
Did the company deliver the project on time and within your expected budget?
It was delivered on time, and the final invoice matched the original estimate.
What tangible results or business impact have you seen since the project was completed?
Our team saves several hours a week, and we have had very few issues since launch.
What did you like most about working with this company?
The consistency. Same team, same standard, from the first week to the last.
Would you recommend this company to others, and would you work with them again?
Yes. They are a reliable AI & Machine Learning partner.

Would happily work with them again

Lotte de Vries / Co-Founder & CTO | Aug 11, 2026

We were happy with the final result. Communication was consistent. We had a weekly call, a shared Slack channel and a project board we could check at any time. When we changed our minds on a couple of features halfway through, they handled it without fuss and were clear about the impact on cost and timeline. Their project manager kept things organised and was quick to flag anything that might affect the timeline.

Since launch, everything has been stable and our team has adapted to it quickly. Documentation at handover was a bit thin and we had to ask for more detail. Overall, a team we trust and plan to keep working with.

Project summary

Callstack was brought in to automate document data extraction that our team was doing by hand. They also took care of integrations with a couple of third-party tools we already used. Overall it was a 2-month engagement.

  • Overall Rating 4.0
  • Quality 4.5
  • Schedule 4.0
  • Project Cost 4.0
  • Willing To Refer 5.0
Project Type:
AI & Machine Learning
Project Cost:
Less than $10,000
Project Duration:
May 2026 - Jul 2026
Business Type:
Mining & Metals
Location:
Eindhoven, Netherlands

Questions & Answers

Please describe your company, your role, and the industry you operate in.
I work as Co-Founder & CTO at Pioneer Mining BV. We operate in Mining & Metals and most of our customers are in and around Eindhoven, Netherlands.
What specific problem or business challenge led you to hire this company?
Our team was spending too much time on manual work. The goal was to automate document data extraction that our team was doing by hand so they could focus on customers.
What services did the company provide for your project?
AI & Machine Learning, including planning, development, testing and launch support.
Why did you choose this company over other providers you considered?
We compared three or four agencies. Callstack asked the best questions and had good reviews from past clients.
How clearly did the company understand your requirements and business goals?
Very well. They asked a lot of questions upfront and turned our rough ideas into a clear plan.
How was your overall experience with their communication and project management?
Good. Weekly calls, regular updates and a shared board meant we always knew where things stood.
Did the company deliver the project on time and within your expected budget?
Yes, on time and within budget.
What tangible results or business impact have you seen since the project was completed?
Customer feedback has been positive, and we have seen better engagement since going live.
What did you like most about working with this company?
How easy they were to work with. They were responsive, honest and genuinely interested in our success.
Would you recommend this company to others, and would you work with them again?
Yes. They are a reliable AI & Machine Learning partner.

Solid Mobile App Development Work With Clear Communication Throughout

Megan Fisher / Director | Jul 03, 2026

Callstack did an excellent job for us. They took the time to understand our business before suggesting anything, which we appreciated after previous agencies jumped straight into building. They were upfront about what was realistic within our budget, which helped us prioritise the right features. When we changed our minds on a couple of features halfway through, they handled it without fuss and were clear about the impact on cost and timeline.

The Mobile App Development work has already made a noticeable difference — tasks that used to take hours now take minutes. We would definitely work with them again.

Project summary

We engaged Callstack to develop a field-staff app with offline mode that syncs back to our main system. They worked alongside our in-house team, which mostly handled business requirements and testing. We worked together for around 3 months.

  • Overall Rating 4.5
  • Quality 4.5
  • Schedule 5.0
  • Project Cost 4.5
  • Willing To Refer 5.0
Project Type:
Mobile App Development
Project Cost:
$50,000 to $149,999
Project Duration:
Feb 2026 - May 2026
Business Type:
Sports & Fitness
Location:
Nashville, USA

Questions & Answers

Please describe your company, your role, and the industry you operate in.
I'm the Director at Lumen Sports, a Sports & Fitness company based in Nashville, USA. I look after our technology and work closely with outside partners on bigger projects.
What specific problem or business challenge led you to hire this company?
We needed to develop a field-staff app with offline mode that syncs back to our main system, and we didn't have the in-house capacity to do it ourselves.
What services did the company provide for your project?
Mainly Mobile App Development. They also helped with the technical planning and a few integrations with our existing tools.
Why did you choose this company over other providers you considered?
A colleague recommended them, and our first calls confirmed they understood what we needed.
How clearly did the company understand your requirements and business goals?
Very well. They asked a lot of questions upfront and turned our rough ideas into a clear plan.
How was your overall experience with their communication and project management?
Communication was good overall and improved further once we settled into a routine.
Did the company deliver the project on time and within your expected budget?
Mostly. One milestone slipped by about a week, but the final delivery was on schedule and the budget held.
What tangible results or business impact have you seen since the project was completed?
We can now handle more volume without adding staff, which was the main goal.
What did you like most about working with this company?
Their attention to detail and the quality of the final product.
Would you recommend this company to others, and would you work with them again?
Definitely. We have already started talking about the next phase.

Exceeded our expectations on quality and communication

Yousef Khan / Chief Digital Officer | May 10, 2026

Honestly, this was one of the smoothest projects we have run with an outside team. When we changed our minds on a couple of features halfway through, they handled it without fuss and were clear about the impact on cost and timeline. Their project manager kept things organised and was quick to flag anything that might affect the timeline.

We launched on schedule and have not had any major issues since.

If you need a team that communicates well and delivers, they are a good choice.

Project summary

Callstack was brought in to add an AI chatbot to our support site that answers questions from our help docs. The work covered requirements, design, development, testing and launch support. The project took roughly 4 months from kickoff to launch.

  • Overall Rating 5.0
  • Quality 5.0
  • Schedule 5.0
  • Project Cost 5.0
  • Willing To Refer 5.0
Project Type:
AI & Machine Learning
Project Cost:
$500,000+
Project Duration:
Nov 2025 - Mar 2026
Business Type:
Real Estate
Location:
Abu Dhabi, UAE

Questions & Answers

Please describe your company, your role, and the industry you operate in.
I work as Chief Digital Officer at Redwood Realty FZ-LLC. We operate in Real Estate and most of our customers are in and around Abu Dhabi, UAE.
What specific problem or business challenge led you to hire this company?
Our team was spending too much time on manual work. The goal was to add an AI chatbot to our support site that answers questions from our help docs so they could focus on customers.
What services did the company provide for your project?
AI & Machine Learning, including planning, development, testing and launch support.
Why did you choose this company over other providers you considered?
We compared three or four agencies. Callstack asked the best questions and had good reviews from past clients.
How clearly did the company understand your requirements and business goals?
They understood our goals quickly, partly because they had worked with Real Estate clients before.
How was your overall experience with their communication and project management?
Organised and transparent. Their project manager kept the project on track and flagged risks early.
Did the company deliver the project on time and within your expected budget?
It was delivered on time, and the final invoice matched the original estimate.
What tangible results or business impact have you seen since the project was completed?
It is still early, but the numbers are trending in the right direction and the system has been stable.
What did you like most about working with this company?
How easy they were to work with. They were responsive, honest and genuinely interested in our success.
Would you recommend this company to others, and would you work with them again?
Yes. They are a reliable AI & Machine Learning partner.

Great team to work with — professional, responsive and reliable

Sanne Bakker / Program Manager | May 05, 2026

Callstack did an excellent job for us. The team asked a lot of questions early on, which felt slow at first but meant there were very few surprises later. The developers were knowledgeable and made a few suggestions that ended up saving us time and money.

The result looks great and performs well, and our internal team found it easy to take over. We are already discussing the next phase with them.

Project summary

Callstack was brought in to rebuild our existing mobile app, which had poor reviews and frequent crashes. Their team handled planning, development and QA, with our product owner signing off each milestone. Overall it was a 8-month engagement.

  • Overall Rating 5.0
  • Quality 5.0
  • Schedule 5.0
  • Project Cost 5.0
  • Willing To Refer 5.0
Project Type:
Mobile App Development
Project Cost:
$50,000 to $149,999
Project Duration:
Jul 2025 - Mar 2026
Business Type:
Aerospace & Defense
Location:
Utrecht, Netherlands

Questions & Answers

Please describe your company, your role, and the industry you operate in.
I work as Program Manager at Evergreen Aerospace BV. We operate in Aerospace & Defense and most of our customers are in and around Utrecht, Netherlands.
What specific problem or business challenge led you to hire this company?
We needed to rebuild our existing mobile app, which had poor reviews and frequent crashes, and we didn't have the in-house capacity to do it ourselves.
What services did the company provide for your project?
Mobile App Development, plus QA and some consulting on how to structure the project.
Why did you choose this company over other providers you considered?
They had relevant experience in Aerospace & Defense and their proposal was the clearest of the ones we received.
How clearly did the company understand your requirements and business goals?
They understood our goals quickly, partly because they had worked with Aerospace & Defense clients before.
How was your overall experience with their communication and project management?
Very responsive. We usually heard back the same day, even with the time difference.
Did the company deliver the project on time and within your expected budget?
Yes, on time and within budget.
What tangible results or business impact have you seen since the project was completed?
It is still early, but the numbers are trending in the right direction and the system has been stable.
What did you like most about working with this company?
Their attention to detail and the quality of the final product.
Would you recommend this company to others, and would you work with them again?
Yes. They are a reliable Mobile App Development partner.

Callstack Delivered a Quality Mobile App Development Solution on Time

Daniel Al Mansoori / Co-Founder | Apr 05, 2026

I would rate this engagement highly on almost every front. Their project manager kept things organised and was quick to flag anything that might affect the timeline. When we changed our minds on a couple of features halfway through, they handled it without fuss and were clear about the impact on cost and timeline. Even with the time zone difference, responses usually came the same day and we never felt left in the dark.

Feedback from our customers has been very positive so far. Overall, a team we trust and plan to keep working with.

Project summary

Our company worked with Callstack to develop a field-staff app with offline mode that syncs back to our main system. They worked alongside our in-house team, which mostly handled business requirements and testing. The project took roughly 6 months from kickoff to launch.

  • Overall Rating 4.5
  • Quality 4.0
  • Schedule 4.0
  • Project Cost 4.5
  • Willing To Refer 5.0
Project Type:
Mobile App Development
Project Cost:
$10,000 to $49,999
Project Duration:
Aug 2025 - Feb 2026
Business Type:
Nonprofit & NGO
Location:
Dubai, UAE

Questions & Answers

Please describe your company, your role, and the industry you operate in.
Keystone Trust FZ-LLC is a Nonprofit & NGO business in Dubai, UAE. As Co-Founder, I was responsible for this project on our side and the main contact for Callstack.
What specific problem or business challenge led you to hire this company?
Our team was spending too much time on manual work. The goal was to develop a field-staff app with offline mode that syncs back to our main system so they could focus on customers.
What services did the company provide for your project?
Mainly Mobile App Development. They also helped with the technical planning and a few integrations with our existing tools.
Why did you choose this company over other providers you considered?
They had relevant experience in Nonprofit & NGO and their proposal was the clearest of the ones we received.
How clearly did the company understand your requirements and business goals?
Very well. They asked a lot of questions upfront and turned our rough ideas into a clear plan.
How was your overall experience with their communication and project management?
Very responsive. We usually heard back the same day, even with the time difference.
Did the company deliver the project on time and within your expected budget?
It was delivered on time, and the final invoice matched the original estimate.
What tangible results or business impact have you seen since the project was completed?
It is still early, but the numbers are trending in the right direction and the system has been stable.
What did you like most about working with this company?
That they were proactive — they suggested improvements instead of just doing what was asked.
Would you recommend this company to others, and would you work with them again?
Yes, I've already recommended them to a couple of people I know.

Great Experience With Callstack on Our AI & Machine Learning Project

Rohan Iyer / Director | Mar 21, 2026

Overall we had a good experience working with Callstack. The team asked a lot of questions early on, which felt slow at first but meant there were very few surprises later. Communication was consistent. We had a weekly call, a shared Slack channel and a project board we could check at any time. Even with the time zone difference, responses usually came the same day and we never felt left in the dark.

We are already seeing better numbers than before the project. A couple of milestones slipped by a week or so, mostly around testing. If you need a team that communicates well and delivers, they are a good choice.

Project summary

We hired Callstack to build a demand forecasting model on top of our sales data. The work covered requirements, design, development, testing and launch support. The engagement ran for about 2 months.

  • Overall Rating 4.0
  • Quality 4.0
  • Schedule 4.0
  • Project Cost 4.0
  • Willing To Refer 5.0
Project Type:
AI & Machine Learning
Project Cost:
Less than $10,000
Project Duration:
Dec 2025 - Feb 2026
Business Type:
Government & Public Sector
Location:
Noida, India

Questions & Answers

Please describe your company, your role, and the industry you operate in.
I'm the Director at Horizon Council Services Pvt Ltd, a Government & Public Sector company based in Noida, India. I look after our technology and work closely with outside partners on bigger projects.
What specific problem or business challenge led you to hire this company?
We had tried to do this internally and it stalled. We needed specialists to build a demand forecasting model on top of our sales data.
What services did the company provide for your project?
End-to-end AI & Machine Learning — from requirements and design through to deployment and a support period afterwards.
Why did you choose this company over other providers you considered?
We compared three or four agencies. Callstack asked the best questions and had good reviews from past clients.
How clearly did the company understand your requirements and business goals?
Very well. They asked a lot of questions upfront and turned our rough ideas into a clear plan.
How was your overall experience with their communication and project management?
Very responsive. We usually heard back the same day, even with the time difference.
Did the company deliver the project on time and within your expected budget?
It was delivered on time, and the final invoice matched the original estimate.
What tangible results or business impact have you seen since the project was completed?
Customer feedback has been positive, and we have seen better engagement since going live.
What did you like most about working with this company?
The consistency. Same team, same standard, from the first week to the last.
Would you recommend this company to others, and would you work with them again?
Yes, I would recommend them and we plan to work with them again.

Skilled Quality Assurance & Testing Team That Understood Our Business

Laura Koch / Founder | Feb 01, 2026

Honestly, this was one of the smoothest projects we have run with an outside team. When we changed our minds on a couple of features halfway through, they handled it without fuss and were clear about the impact on cost and timeline. They were upfront about what was realistic within our budget, which helped us prioritise the right features.

Since launch, everything has been stable and our team has adapted to it quickly. Happy to recommend them.

Project summary

Our company worked with Callstack to run performance and load testing ahead of a big launch. They also took care of integrations with a couple of third-party tools we already used. We worked together for around 6 months.

  • Overall Rating 4.5
  • Quality 4.5
  • Schedule 4.5
  • Project Cost 4.0
  • Willing To Refer 5.0
Project Type:
Quality Assurance & Testing
Project Cost:
$10,000 to $49,999
Project Duration:
Jul 2025 - Jan 2026
Business Type:
Media & Entertainment
Location:
Munich, Germany

Questions & Answers

Please describe your company, your role, and the industry you operate in.
I'm the Founder at Pinecrest Pictures GmbH, a Media & Entertainment company based in Munich, Germany. I look after our technology and work closely with outside partners on bigger projects.
What specific problem or business challenge led you to hire this company?
We had tried to do this internally and it stalled. We needed specialists to run performance and load testing ahead of a big launch.
What services did the company provide for your project?
Quality Assurance & Testing, plus QA and some consulting on how to structure the project.
Why did you choose this company over other providers you considered?
Their pricing was fair and they were honest about timelines instead of just telling us what we wanted to hear.
How clearly did the company understand your requirements and business goals?
Very well. They asked a lot of questions upfront and turned our rough ideas into a clear plan.
How was your overall experience with their communication and project management?
Very responsive. We usually heard back the same day, even with the time difference.
Did the company deliver the project on time and within your expected budget?
It was delivered on time, and the final invoice matched the original estimate.
What tangible results or business impact have you seen since the project was completed?
It is still early, but the numbers are trending in the right direction and the system has been stable.
What did you like most about working with this company?
How easy they were to work with. They were responsive, honest and genuinely interested in our success.
Would you recommend this company to others, and would you work with them again?
Yes. They are a reliable Quality Assurance & Testing partner.
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