Trade In Not Credited

In March I traded in an Apple Mini 13 and received a $500 credit. For 5 months I called/chatted with Xfinity asking about my credit. I kept getting told that they haven't got confirmation that the phone was accepted. Last month they gave me a $200 credit and I thought it was for the back trade in credits and it all got straightened out.

I got my new bill for September and the full device payment is on the bill $34.58. I went on a chat with Xfinity and she told me that it's because I canceled the number on the new phone and that made me forfeit my trade in credit. This is the first time I'm hearing this in 6 months that I've called or chatted with them. When getting the new phone, I didn't want to have a new number so I called and asked if I could keep my old Xfinity number and not once was I told it would make me forfeit my trade in credit. I spoke to a supervisor today 8/8/2025 and he told me the case is closed and nothing will be done. 

It's not right Xfinity gets to keep my my Iphone Mini 13.