You can add users to the Teams app as a Partner/Reseller (through the Portal), although it requires a two-step process to allow the Microsoft Enterprise to authenticate the changes made in Microsoft Office.
Step 1. Reseller Adds/Deletes User(s)
- Select the Enterprise you want to add a user into.
- Navigate to Enterprises. Then select … icon on the far right (under action), select Assign DIDs
Step 2. User Sync
The Microsoft Global Admin or the Microsoft Teams Service Admin/Skype Admin of the Enterprise MUST sign in to the Enterprise portal and perform a sync to complete the Teams Registration and active Teams Calling.
User Sync task can be performed by the Service Provider if consent for Enterprise Management is granted by the Enterprise Admin.