How to escalate a complaint

I would give zero stars if possible. Customer with att for 20 years switching to T-Mobile was worst mistake ever. Sales lady over phone gave broken promises. Porting numbers in over the phone was an absolute joke. The incompetency of these employees is ridiculous. Was made to go into store twice where the in store people despise the tele sales. Made to go back to store a 2nd time the lady on phone told me they needed to send some verification pin to the lady in the store. The lady in the store had no idea what they were talking about.  Horrible customer service since they're not on same page. They screwed up importing my numbers put my number to my brothers cell phone. Spent 6 hours with no phone and another 2 and half hours trying to port in the same numbers for my tablet and watch. Was supposed to import old numbers for tablet and watch to receive rebates and they screwed that up as well. Was conned into buying new phone because they didn't check if my phone was unlocked yet before they ported it.. All I received was $50 off on my first bill. I spent 2 hours getting bounced back and forth from the rebate team to customer care where literally nobody will let you speak with a supervisor. I'm sure all these rebates will never come in either after reading all these reviews and I'll be spending countless more hours not getting anywhere  I need to inquire about filing a dispute and dropping them asap. BEWARE DO NOT SWITCH FROM ATT! These are scam artists. WORST purchasing experience of my entire life.