How did we implement the CALL FROM TEAMS service in Combis?

After a long time, the paradigm of using fixed telephony changes. The change is big, but not complex, on the contrary, it will simplify use and change the way a desk phone is perceived – there is no need for it anymore!

Because we have Microsoft Teams!

Starting point – why have we decided to implement this service?



Combis has been cooperating successfully with Microsoft for many years, continuously expanding its portfolio of services and solutions based on Microsoft technology, and when Microsoft announced an extension of Teams platform functionality called Direct Routing, which allows calls from Teams, a team of experts for Unified Communications solutions from Combis immediately became interested in the service and set out to study all the functionalities of the solution.

The best way to get to know a solution in depth and to find out about all the advantages and pitfalls that the implementation of such a solution brings with it, is internal application, the so-called ‘in-house’ experience, especially if it is a complex implementation that requires continuous feedback from colleagues working with the solution.

Microsoft Teams, as a collaboration tool, has been actively used in Combis for several years, and this upgrade was an opportunity for Microsoft Teams to further evolve and take on the role of a complete Unified Communications solution.

All the reasons for implementation are on the table, the decision has been made – now, what’s next?

Some of the initial preconditions for implementation within Combis were:


  • certified Session Border Controller (SBC) by Microsoft
  • SIP trunk with a telephone service provider
  • physical infrastructure which includes:
    • sufficient data center resources
    • firewall
    • quality of service at the network level
  • configuration of MS Teams in O365
  • service supervision and redundancy

The initial situation in Combis was as follows:


  • About 300 numbers / telephone connections…
  • MS Skype for Business and Cisco Call Manager
  • Combination of E5 and E3 Microsoft licenses

“What means the most to me is that it’s easier for me to do work while I’m out of the office or on a business trip. No matter where I am, in a hotel room, or at the airport, on a park bench or a terrace, as long as I have internet access, I am available to everyone in the same way as if I were sitting in my office.”


Andrej Anđelić, ICT Sales Manager, Hrvatski Telekom

“Since I spend more than half of my working day ‘on the phone’, I was literally thrilled with Call From Teams. I don’t have to constantly pick up the phone, type in numbers, it may sound like I’m a little bit spoiled, but it’s only now that I see how much little things can cheer a person up. Thank you colleagues, you have definitely made my business days better.”


Zorica Crnčić, Secretary of the Management Board, Combis

Implementation in 5 steps:


MS Teams configuration in O365


Firewall configuration for SBC connectivity with MS Teams cloud service


Oracle SBC installation and configuration for SIP trunk reception from telecommunications service provider


Connecting SBC with MS Teams Tenant


Detailed testing and troubleshooting

Find out all about the service

How did we overcome the challenges?


After the successful establishment of the first call to the fixed line, the team of experts working on the implementation was not completely satisfied with some functionalities that were not at a satisfactory level, such as putting the interlocutor on hold, transfering calls to another number, redirection….


“The problems we encountered were different, from breaking a call during transmission, one-way audibility when transferring a call, returning a call from hold, misrepresenting a calling number, interrupting a call when setting up a teleconference,…


Each of these and other minor problems after mass implementation can become a big problem and the user can very quickly lose the will to use the service, which would cast a big shadow on the effort and raise doubt for implementing the service. We knew that we had to eliminate all problems and overcome all challenges. Our goal was for every aspect of fixed telephony to work perfectly”, said Darijo Puntarić, the engineer who worked on the project, and added: “After a long period of solving even the smallest problems, we could finally say – it works! We can go on with the mass implementation!”

Did you know?


Until now, most of these implementations required having on-premises infrastructure, which many companies refused because the implementation costs did not stop at the costs of equipment and services of the system integrator, but also included the costs of infrastructure storage in the data center. With the CALL FROM TEAMS service there is no need for having your own infrastructure!


Still hesitant?


Maybe you are not ready for a complete transition to MS Teams and still want to keep your own PBX infrastructure for part of the business? No worries, our solution allows you to connect your existing PBX system to MS Teams platform for voice communication and calling.

“Microsoft has previously offered calls to fixed telephony in its portfolio as its service, the so-called Microsoft Calling Plans, but only for a limited part of the market. Since this option is not available for Europe, we decided to test Direct Routing and very quickly became aware of the benefits of the new solution”, said Darijo Puntarić, System Engineer Specialist from Combis.


“MS Teams is becoming the central application of the smart workplace, whether you work from the office or from home, but one of the functionalities that was constantly excluded from all smart systems for integrating work environment tools was fixed telephony, but fortunately, it is now a thing of the past, and our CALL FROM TEAMS service is the best proof of that”, points out Jasmin Baborac, Head of the Business Solutions Department for Unified Communications in Combis.


Feel free to contact us for even more information, we love to talk about the benefits of our service!

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