lost phone at tmo grc fort worth, tx

First time happing to us but same issue.  For the past couple of years we have bought and traded in our phone online. No problem.

This time we received the new phone.  I boxed up the trade in and correctly packaged and labeled it like I always have.  I tracked the box until it showed delivered to Dallas TX.  2 months later the trade in phone was never checked in at the warehouse.  After 5 phone calls to T-Mobile I was finally told I would have to file a claim with the USPS to recover my money from the trade in phone.  Meanwhile the charges for the traded in phone continue to appear on my bill.  I will never mail in a phone again.