To update a phone number for two-step authentication in Microsoft Entra ID, you can follow these steps:
- Sign in to the Microsoft Entra admin center as at least an Authentication Administrator.
- Navigate to Entra ID > Users.
- Select the user for whom you want to update the phone number and go to Authentication methods.
- At the top of the window, select + Add authentication method.
- Choose Phone number from the method options.
- Enter the new phone number, including the country code, and select the appropriate phone type (Mobile, Alternate mobile, or Other).
- Click Add to save the changes.
Users can also update their own authentication methods by going to My Sign Ins | Security info and selecting the phone number option to change it.
Make sure that the phone number is unique within your tenant, as using the same phone number for multiple users will result in an error.