Premisses: 

• you have an office 365 account
• Multi Factor authentication is allready set up

1. Go to https://myaccount.microsoft.com/?ref=MeControl 
2. Login with your Microsoft 365 credentials ( company email and password) 
3. In the My Account screen, go to the section "Security info" and choose update info
   
4. From this screen you can adjust your phone number,  add or remove authentications.
   Note however: If you remove all, you might be prompted to start all over again configuring Multi actor authentication. No multifactor authentication is not allowed.