When you try to sign in using Microsoft MFA, the phone number listed for text messages and/or voice calls is not right.

You have not updated your Microsoft MFA methods to remove the old number and add your new one.

First, follow the setup instructions for MFA, in the "Alternative options" section, to add your new number. Then, remove the outdated number from the list.

Outcome

When you sign in, the correct phone number shows up.