This functionality will depend on your Operator. If you are assigning numbers to Operator Connect or Operator Connect Mobile users, you may or may not be able to assign or change the associated emergency location. To assign or change the associated emergency location, under Emergency location, search for and then select the location. In the Edit pane, under Assigned to, search for the user by display name or user name, and then click Assign.

On the Phone numbers page, select an unassigned number in the list, and then click Edit.

In the left navigation, click Voice > Phone numbers. This is usually the account you used to sign up for Microsoft 365. Open the Microsoft Teams admin center and log in with a user that is a Global admin. To assign a number by using the Teams admin center: When assigning a phone number to a user, make sure the phone number and the usage location of the user are of the same country/region. If you want to assign a Calling Plan or Operator Connect phone number to a user or resource account, you must ensure that any phone number stored in the msRTCSIP-Line attribute on the user or resource account object in the on-premises Active Directory has been removed, and the change has been synchronized to Microsoft 365. This note applies to customers who have a hybrid deployment with an on-premises Active Directory.

Microsoft account phone number change