If you are using Microsoft’s Calling Plan license you will need to remove it before adding a Direct Route to your PBX. Microsoft has a trial license that includes Calling Plan so it is a common way Enterprises first test out the service.
If this license is present you will receive an error that says "Cannot modify the parameter: "OnPremLineURI" because it is restricted for the user service plan: MCOProfessional,MCOMEETADD,MCOEV,MCOPSTN1."
Here is a step by step process to ensure that it is disabled.
Ensure that you have assigned per Group A a User and Add On License to any Users who will have the Connector activated. Navigate to Users>Active users>(future TeamMate Connector User)
After selecting the User Navigate to Licenses and Apps
Select App, then Dropdown Menu will appear
Ensure that the Calling Plan is unselected
Save changes when ready
Once Microsoft Admin confirms those licensing changes have occurred for the User you will be able to link Teams to the PBX using the Connector.