Where is my credit

I went to a local Xfinity retail store.in January 2025. The deal was trade in my iphone 14 for a new Iphone 16 and set up a new line with Xfinity Mobile. My wife was with me and traded in her phone, too. We watched them clear or old phones, transfer info to our new phones, and left. When our first bill came, we went back to the store to get ask why there was no credit for the phones we turned in. Now after 6 trips to the store, numerous "tickets" submitted, speaking with 3 associates, and assistant manager and the store manager, I received a call from the store manager saying they have no record of nor can they find the 2 iphone 14s we handed them. Sorry, no credit. hands are tied. What course of redress do I have? What should my next steps be?