UPS lost my trade-in. t-mobile people refuse to do anything

In April, my wife upgraded her phone and activated it at the T-mobile store at 5980 Jericho Tpke in Commack. When she received the phone and the return label for the trade-in, she brought it to the store for them to examine to make sure it was good for trade-in and to avoid any issues. UPS lost the phone, and now T-mobile is not honoring the trade-in. My wife reached out to UPS and they said t-mobile had to file the claim because they were the shipper. Customer service has been giving us a run-around. First, we called and the call center customer service people took all the information, confirmed that this happened and then never called back. She called again and they told her she had to go back to the store. She called the store was told she needed to speak to a manager, who never called back. She went down to the store and they told her she had to go to corporate store. Today she went to the corporate store and sat with a woman ( Alison B. ) who spent an hour on the phone with someone internal, only to be told she had to go back to the original store and to talk to the assistant manager, because they were supposed to enter the trade-in into t-mobile systems. Alison called over to the store to say my wife was coming back. My wife arrives at the store to be told that the assistant manager left and she needed to come back tomorrow ( Monday, July 6 ) and speak with the store manager Hassan. We are getting bills for the full price of the phone. This is nuts already. Unreal that customer experience isn’t empowered to take ownership to solve a customer problem, or that customers are expected to chase down solutions to problems caused by the store employees to begin with.