While SimpleVoIP can adjust many of its Enterprise Settings, it cannot Enable Calling because it involves Microsoft PowerShell credentials. This MUST be done by the Microsoft Admin.
As the Microsoft Enterprise Admin, navigate to User Management >> Manage Users
Select Action >> Enable Calling for a user.
There will be a loading bar underneath the Users heading indicating that the user is being enabled in PowerShell.
The Teams Registration for the user will display a green checkmark upon successful completion. The Teams Admin will also receive a success message via email