More than one authorized user

You are right about that, but T-Mobile does allow for 3 users on the account (the Primary person of whose account is in their name and two authorized users).  I'm seriously wondering why you're having such a hard time getting this straightened out if you've requested to be added several times.  Is the account in your husband's name? He would need to be the one to call in and request the change as only the primary can add and remove authorized users.  That's literally the only reason I can think of that adding your name to the account wouldn't be successful.  Is he active on social media? If so, I'd recommend reaching out to T-Force to have this situation fixed very quickly.