T-mobile charging me for returned phone

So my s23 ultra broke back in July, i used the insurance. Tmobile sent me a refurbished phone and a prepaid ups label to send the old phone back.  After about a month I get a notification that I owe 1400 dollars for a device I never returned. I called customer service, gave them the tracking number that ups says was delivered to Ft Worth Texas. Customer service calls me back in August saying they still haven't located the phone and pushes billing out to October.  I get a call from customer service this month and saying the IME number on the phone that was received was not the correct phone so now they are trying to stick me with the bill. The phone I returned was 100 percent the phone I got from the local store. ¿Qué hago?