As you are likely aware Microsoft Teams Business Voice comes in two versions in the UK, with Calling Plan and without. At the time of writing Microsoft Partners who have the Small and Midmarket Cloud Solution competency have Business Voice included as part of their Internal Use Rights (IURs). The UK IUR licensing comes with Microsoft Calling Plan. I mention this as the scenario discussed below applies to both standard and IUR Business Voice licensing.
Even though they have Microsoft Calling Plan use rights some customers/partners may still want to assign an on-premises phone number to one or more of their users. An example scenario might be a Microsoft UK Partner with Business Voice IURs who wants to use their own Direct Routing service for PSTN calls.
This is perfectly legal but even if Direct Routing is set up correctly and the user is assigned their on-premises number I’ve seen this configuration fail. Why? The short video below contains the answer.
The resolution may seem trivial with hindsight but it’s an easy step to overlook!