Thanks for posting your question in the Microsoft Q&A forum.
Go to https://myaccount.microsoft.com/ and sign in, Navigate to the Security
section, usually found in the top menu bar and look for and select Advanced security options
or a similar option related to security settings. In this section, you should be able to view and edit your authentication methods, including phone numbers.
Select the option to add a new phone number. You'll need to verify this new number, usually by receiving a code via text or call.
Please don't forget to close up the thread here by upvoting and accept it as an answer if it is helpful