T-mobile is lies

I have had nothing but headaches with Tmobile. i had a promotion and got 3 new iphones and sent in 3 trade ins. for the past 8 months have been getting charged full price for 1 of the phones. contacted customer service about 30 times. They confirmed that they received the 3 trade ins and they will get this issue resolved and never do. They always say they will follow up and never do. Have all the screenshots of the lies from customer service. next up i will have to contact a lawyer. Tmobile stole my iphone. and my time since i have spent numerous hours with customer service and nothing gets fixed.