Trade in

I’ve been on the phone with so many representatives about a trade in device error. 
I sent off 2 I phone 14s - one my husbands and one was mine, my husband‘s being the more expensive one. 

we sent both off exactly how it was supposed to and somehow my husband was “lost” along the way despite me getting an email saying that the trade-in was accepted, and it would be applied to our balance which it still hasn’t. my phone was accepted for trade in and the balance was applied but somehow my husbands never applied? I traded in the phones at the end of March. It’s now the end of August, and I have gotten the runaround by so many people. I lost count how many saying that they would escalate it and that a ticket has been opened and that they would solve it in a few days and it never has happened. They’ve done that to me multiple times now. 

I’m at the point where I’m convinced they’re just waiting for me to give up so that I just keep on paying the amount but I have time so I’m really not gonna quit. My family has been using Xfinity for years. The only reason we switched from Verizon to Xfinity was so that we could be altogether and I heard pretty good things about Xfinity but after this, if they don’t give me money for my trade-in, I’m gonna be really upset. I could’ve sold it on Facebook marketplace and just had cash. The phone had over 500 GB on it. My husband always gets extra gigs so the phone was worth a good amount of money.