usps lost next return package
I recently ordered iphone 8 plus and returned the phone on 10/05/217 which is the same day I received it.
I also called the at&t and they said didn't received the package.
I have the return receipt and I checked the tracking, it shows usps received and not delivered .
I called customer service and they say contacted the store to help with retail support team to reverse the upgrade,
however, its been after 14 days and they refused to reversed it.
what should I do on the next step?