Trade-In Rejection (ERROR) and phone being shipped back cannot be located

I purchased a new phone from Xfinity mobile and selected to trade in my old device (iPhone 13 Pro), with an estimated trade-in value of $830.  I prepared my trade-in according to the instructions provided, took a video of the General > About screen of the trade-in as proof of the phone I was sending back (on 9/29/23), and packaged and shipped the phone.  The phone was in great condition, was originally purchased from Xfinity, and was shipped back for trade-in assessment in the original iPhone box.

I tracked the device via the USPS tracking number provided where the shipment sat at a postal office in York, PA for days before being claimed.  I received no email confirmation that the phone was received/being processed nor did I receive one when the phone was rejected due to a "serial number mismatch". I had to login to my Xfinity account to check the status to see that it had been rejected and the old/trade-in phone would be shipped back "immediately".  It has been over 2 months and no one is able to tell me where my old phone is, when it will actually be sent back to me, or a tracking number for purposes of identifying where the phone is located, just that it's "being shipped back to the customer".  I have chatted multiple times with Xfinity, sat on hold for hours (currently over 2 hours on hold waiting to talk to a supervisor), and am now out the $830 trade-in value for a phone that is NOT a mismatched serial number (of which I have proof) and out the hundreds of dollars I could have made by selling the phone myself. When it was sent in, the phone was in great condition and I have no idea the conditions of which the phone is currently being stored in or where it is even located.

I have copies of the original iPhone 13 Pro order receipt from Xfinity noting the IMEI and ICC ID numbers, the "customer copy" of the trade-in instructions (which identifies an IMEI number which was on my phone but identified as IMEI 2), and a screen recording of the General > About screen of the phone that was traded in.  The recording I took of the General > About section of the iPhone prior to sending back matches the IMEI and ICC ID codes on the original iPhone 13 pro order AND identifies the matching IMEI 2 number from the trade-in paperwork.

No one from Xfinity has been able to help me after several attempt and several hours of my time just trying to locate where the trade-in phone is located that, according to my Xfinity account, is being "sent back immediately". Two months later and I am STILL waiting for the phone or for someone to be able to provide tracking information for the device.... just that it's being "shipped back to the customer".  Completely unacceptable and terrible business practice and customer service.