How to Change a Microsoft 365 Administrator Without the Former Admin's Phone

Sign in to the Microsoft 365 admin center (admin.microsoft.com) using the secondary Global Administrator account.

Navigate to 'Users' and click on 'Active users'. Search for and select the former administrator's account.

In the user pane, click on 'Manage multifactor authentication'. Select the former admin's account and click 'Require selected users to provide contact methods again'. You can also delete their existing app passwords.

If you are setting up a replacement administrator, go back to 'Active users', select the new user, click 'Manage roles', and assign them the 'Global Administrator' role.

Go to the official Microsoft Support website and find the business support phone number specific to your country or region.

When calling, clearly state that you are entirely locked out of your Microsoft 365 tenant and need to speak with the Data Protection Team for admin account recovery.

Provide the requested verification details. This usually involves proving you own the custom domain via DNS records and verifying company billing information.

Once Microsoft grants access, immediately set up a new Global Administrator account and update all authentication methods and contact information.