Xfinity lost my Iphone trade-in

Apparently this is not just isolated to me and others have experienced significant issues over Iphone trade-ins given what I'm seeing on this forum.

Over a month ago I qualified for an early upgrade without paying off the remaining Iphone balance. I did this in store and handed the employee my phone who made sure it was in a good condition to qualify for the upgrade. Last week I then get charged for the remaining balance ~$500 out of nowhere without any warning and after spending over an hour with customer service and getting bounced person to person, all that was said was I needed to handle this with the store directly and the customer service line could not help me. I then go to the store and they can't even confirm that they received it or even sent it out after I HANDED IT PHYSICALLY to the employee that day. I asked them to look at the camera footage to confirm this and was told they aren't allowed to do that. So now I'm stuck taking the financial hit despite going through all the proper steps of upgrading my Iphone and no one from Xfinity is taking any responsibility over this matter. In fact the store couldn't even get a hold of anyone on their end to help with this issue so now the customer service line and the store are pointing fingers at each other with again NO ONE TAKING ANY RESPONSIBILITY over the fact that Xfinity lost my trade-in after I physically gave it to them. To make matters worse I didn't even see the employee wipe my phone before taking it to the back of the store. So it is completely possible they have employees taking iphone trade-in's and selling them off to the side or actually damaging the phone after the trade-in and the customer now has to pay for this fraud. I would like a refund and Xfinity take responsibility over their mess-up and actually confirm this phone was received and wiped and if not take more serious steps to address losing customer personal information or actual fraud.