Initial situation
When the project began, the telephony environment was based on a legacy architecture, typical of organizations that have evolved in successive stages.
Skype for Business still in place. An on-premise Alcatel infrastructure managed part of the traffic, particularly Hunt Groups. Several remote sites were interconnected. Special 0800 numbers had to be maintained with strict service commitments. And at the heart of the system, a SBC ensured the continuity of SIP traffic.
The system worked, but it was based on end-of-life technologies and a fragmented architecture. The tools coexisted without any real unification. Administration was more complex than it needed to be, and the transition to a modern model was becoming inevitable.
At the same time, the company wanted to modernize its customer service by implementing Dynamics 365 Contact Center.
But to build a robust contact center, the foundations first had to be modernized. Before adding a new application layer, the telephony itself had to be transformed.
The project was therefore conceived as a comprehensive, gradual, and controlled transformation.
Goal
The goal was not simply to migrate users from one tool to another.
The aim was to rethink the voice architecture as a whole.
The strategy had several objectives:
Replace Skype for Business Microsoft Teams .
Gradually migrate the Alcatel infrastructure to a cloud model cloud with Microsoft 365.
Maintain the SBC in high availability to protect the investment and maintain routing control.
Maintain special numbers and operator commitments without interruption.
Prepare the organization for the integration of Dynamics 365 Contact Center.
But beyond the technical aspects, the project also had to guarantee:
Service continuity at every stage.
Smooth adoption by users.
Autonomy for IT teams.
A scalable and sustainable architecture.
The ambition was clear: to move from a legacy telephony environment to a unified, modern platform ready for advanced contact center uses.
Concept
The project naturally fell into two major complementary stages.
1. Modernization to Microsoft Teams
The first phase consisted of finalizing the migration from Skype for Business Microsoft Teams .
Users were migrated gradually, with Direct Routing enabled. The SBC high-availability SBC was integrated into the Teams architecture, ensuring full continuity of SIP flows and proven resilience.
Switchover, resilience, and service continuity tests were carried out to ensure each stage was secure before rolling out the system across the board.
At the same time, the Alcatel infrastructure was modernized.
The old Hunt Groups have been replaced by Teams Queues and Auto Attendants. This change has made it possible to centralize management in Microsoft 365, simplify administration, and improve the user experience.
Remote sites have been integrated into the new architecture. 0800 numbers have been migrated in close coordination with the operator to ensure proper call presentation, correct routing to Teams maintenance of existing SLAs.
The transformation was not limited to technology. Short, practical user guides were distributed to facilitate the transition. Administrators were trained in managing call queues, auto attendants, and Direct Routing. This approach enabled rapid adoption and a significant reduction inmigration incidents.
Once this initial phase was complete, the organization had a modern, stable, and unified telephony system under Microsoft Teams.
2. Integration of Dynamics 365 Contact Center
With this foundation now stabilized, the second phase of the project could be launched: the implementation of Dynamics 365 Contact Center.
At that time, native Teams for D365 Contact Center was not yet available. So we deployed an architecture based on Azure Services in Direct Routing.
The architecture was based on a clear chain: operator, SIP Trunk, SBC , Azure Services, then Dynamics 365 Contact Center.
The project covered four distinct environments: DEV, TEST, UAT, and PROD.
Each had its own dedicated configuration, separate TLS certificates, isolated routing, and independent technical validations. Managing multiple domains and certificates was a key factor in ensuring strict isolation between environments.
The architecture was also designed to be hybrid: some flows were directed to Dynamics 365 Contact Center, others to Teams Queues, depending on business needs. This approach allowed for maximum flexibility while optimizing license usage.
The migration carried out in stages, with analysis of numbering plans, comprehensive SIP testing, verification of codecs and certificates, failover testing, business validation, and then migration of numbers into production with enhanced monitoring.
Each phase was validated before moving on to the next, ensuring a secure production launch.
Result
At the end of the project, the organization transitioned from a fragmented, legacy telephony environment to a unified, modern, and scalable architecture.
Skype for Business been fully migrated.
The Alcatel infrastructure is in the final phase of decommissioning.
The SBC is fully integrated into the Teams ACS architecture.
Hunt Groups have been modernized via Call Queues.
0800 numbers and remote sites are integrated and secured.
The four Dynamics 365 Contact Center environments are operational and isolated.
The company now has a consistent, stable voice platform that is ready for future developments in the Microsoft ecosystem.
This project illustrates that a successful contact center transformation does not begin with the agent interface, but with a solid telecom architecture.
Modernizing the voice layer, securing routing, supporting users, and structuring migration it was this comprehensive approach that enabled the successful end-to-end transformation.
We share your challenges, we accompany your changes
If you'd like to find out more about how Lambert Consulting can help you transform your customer relationship management with advanced CRM solutions and artificial intelligence, please don't hesitate to contact us.
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