add a limited authorized user

I'm not trying to add a line. There are only myself and my father who are able to make changes to the account. My problem is that when I ask questions the tmobil reps don't answer and they don't know how to subtract and they allowed an unknown person to sign my name in a store. Not a digital name but a hand written signature of me and I didn't authorize it neither did my dad and its identity theft. What kink fixes those issues? What kind of user do I need to be to fight identity theft and fraud on my account? Neither being a PAH or a full accsess user on the phone, in person or on messages has accomplished fixing that. Hopefully a t mobil rep will read this and call my phone and actually fix it because while I thank you for your suggestions me doing anything about adding somebody else will not fix math identity theft or the fact that Customer care team members are Exstremely rude and if you sign up for Netflix on us or any other promotion they charge you unless you catch it. It will also not explain how last month the bill was $80 for the plan and adding a free line with a free phone brought the plan up to $200.