T-mobile refusing to give me my credits from a promotion I qualified for

Same has happened to me. Promo was in April 2023. Free IPhone 14 for new and existing customers. Needed to upgrade to eligible 5G. Done. Sent in 3/IPhone 11's in mint condition for rebate. Done. That's a joke and misleading. Basically, putting a down payment on the new phone like a car dealership. I asked tons of questions. We're being recorded,"Correct." Yes. Still the promo for the monthly discounts have not been applied since I switched plans, and sent in my 11's. I've called. Chatted. Screenshot the chats because it's now disappeared from my app. The person I was chatting with took offense to my concerns. I was not rude. Yep. Got it on screenshot. I'm sorry, but if I took advantage of you, how do you think you'd feel? I've been with TMobile for 4-5 years. Never experienced an issue. Clearly, this is the pitfall. Trading in and upgrading your phone. I should have done what I always have done, and purchased the phone through Apple. Now, what do I do? My IPhone 11's gone. I have no intention of paying this bill, as is, because IT IS NOT the agreement we made. Computer glitch, I was told by the recent representative who's waiting for a supervisor to fix the problem. Recorded call. Then, fix it TMobile!