Currently only the USER can change their MFA AFTER logging in, which means when Twilio is having message delivery issues, your users cannot log in and you cannot adjust MFA type to Authenticator would allow them to work... How about you add an MFA tab inside of the User Management section so that Administrators can reset the MFA when someone gets a new phone number or needs to change to Authenticator. When you hit MFA reset it would allow a log in with known password, then the NEXT SCREEN would require MFA enrollment selection for either Mobile or Authenticator (preferably BOTH) to proceed to login! This is the way.