Poor customer service

Anyone know how to reach corporate? I have been having 7 months worth of poor customer service and been reassured every month T-Mobile would fix their errors from September only for it to remain messed up on my bill. I have talked to customer service representatives over the phone, over chat, talked to supervisors. I filed with FCC and BBB. Tired of being lied to and getting the run around. I get told things were put in incorrectly and paperwork was filed to fix it and that’s been the last two months. 7 months is patient enough, I want to talk to higher up.