Run Around regarding Trade In Credit

I traded in my iPhone 8 Plus in August 2020. I have made several calls to AT&T. I have been on the phone no less that 6 hours in total trying to resolve this issue. It is still unresolved several calls to customer service as I have not received any credit as promised. I asked for my phone back and they said it could not be shipped back. Has anyone else had this issue?Att’s customer service is horrible!!!!!! I am truly regretting moving my service here!