If you're using an organisation email: Please contact your IT Administrator to reset your authenticator. The next time you sign in to your account, you'll have the option to choose your mobile number as the authentication method—provided your organisation allows authentication via mobile number. You can refer to the following article, which outlines the process for setting up your mobile as an authentication method: đŸ”— Setup MFA with Microsoft Authenticator
If you're using a personal email: Follow the article below to guide you through resetting your authentication method from the authenticator app to your mobile number. This will allow you to remove the Authenticator app from your phone: đŸ”— How-to-Reset-Multi-Factor-Authentication-MFA-in-Microsoft-365 : [Select Mobile Phone in step-6 of "Add a method"]