If he is the account owner and you are only an authorized user, unfortunately, there's not much you can do. He has the option to suspend or cancel your line. The only problem he may have with canceling the line is if there's installments on your phone which he will be billed for in bulk
If you're on good speaking terms I suggest you ask him to release your line by visiting att.com/tobr and give you billing responsibility of your line so you can keep your line number and get your own account with AT&T.
I have a no contact protection order. He has been charged with domestic violence. So there is no contact between us. I'm not sure if my protection order would help but I'll prob go get different service some where else. Thanks