Tmobile lost my trade in and is not honoring trade credit.What can I do?

I'm dealing with the exact same thing. Most of the replies you have received are incorrect. T-Mobile does use the tracking numbers to verify the phones. I had mine appraised and boxed at the t-mobile store. They told me to make sure that I had it sent from the USPS desk and not to drop it in a mailbox as this could happen. It did of course happen to me as well. I just spent hours on the phone with t-mobile and sent them proof of the shipping dates and tracking numbers. They verified everything and apologized. I told them I just wanted my S21 back and a refund for what they overcharged me (they withdrew me from the promotional program because they didnt think they had my phone) . When I called them (after being charged $50 over my bill two months back to back) they used the info I provided and found my phone. They verified it was in there warehouse but basically told me I was screwed. They said they cannot return my phone and that they will only refund $50 as a courtesy and manually escalate the issue. My promo said that the phone must be mailed no later than the 17th in order to arrive by the 30th. I mailed it on the 13th and provided a tracking number and they still refuse to honor our deal. I am literally taking the $50 refund and want my old phone returned in some form and am done with T-Mobile. I have been a customer for YEARS and have been on auto-pay but never have I dealt with MORE BS than this company. 1.7 stars and now I know why. It's all scams and vague rip-off schemes. I provided actual proof to the customer service supervisor and she apologized and acknowledged I was right and had met the promo regulations but there was nothing they could do. That they deal with this all the time and they are limited to what they can do. $50 refund and that's it. I cannot do business with a company that does not honor there word but holds us to ours. No way and I encourage anyone who reads this to do better for themselves as well.