If you’re porting your numbers to Calling Plans, Operator Connect, or a new Direct Routing provider/trunk, you’ll need to plan when to assign those numbers to your users and auto attendants.

This blog post also applies to Direct Routing scenarios where you’re not changing PSTN providers but are directing the numbers from a existing PBX to Teams.

For Calling Plan and Operator Connect scenarios, you’ll submit your port request and once it’s approved (called FOC or firm order commit), those numbers will appear in TAC. At this point, you can change usages from user to voice app or conference, and you can assign them to users.

But should you? Maybe!

You can go ahead and chance number usages to voice app or conference (or back to user if you need), this has no impact on anything ongoing.

However, if you are moving your users to Teams in batches, you will need to assign numbers carefully. The first thing that Teams considers when a number is called from Teams, is whether Teams “owns” that number. If Teams does not own the number, it is sent out to the PSTN.

Consider a scenario where the Seattle office’s phone numbers port to Teams. If the Portland office’s numbers are porting in a few days, you could go ahead and assign those numbers to the Portland users. However, should a Seattle user attempt to call a Portland number, the Portland user’s Teams will ring, not their old phone. Teams owns the number, so routes it directly to the user with the number assigned to them.

This may not be a problem in your organization if your users are expecting Teams calls before their scheduled port date and time. Most often, I find that this is confusing to most users. The other challenge could be with end user devices. If your users will be using headsets they’ll be fine, however if you have to deploy Teams IP Phones you’ll need to ensure those are in place before you assign numbers. You may not be able to place those phones and connect them to a PoE ethernet run without first unplugging the old phone… which means they won’t receive calls from the PSTN.

When to do the number assigment

I recommend assigning the phone numbers a few hours before the port date/time. I also recommend scheduling a port for either first thing in the morning or at the end of the work day, whereever possible. If the port is scheduled for first thing in the morning, numbers can be assigned the night before. If the port is scheduled for last thing in the day, you can assign the numbers right before the port and you’ll have some buffer time should the assignment take a while.