I was sent to collections for a phone I turned in a year ago

Hola,

I switched from T-mobile to AT&T last year. I turned my phone in and a few months later, I get a collection notice from a  bill collector for $900. I called T-mobile customer service and they said the phone has not arrived yet. So I asked them why I was sent to collections. The lady told me she would take it out of collections while they wait for the phone to arrive at the warehouse.

Two months pass and I get another collection notice from a different bill collector. I call customer service again and this time the CS Rep asked me if I was on a lease/jump program. So I tell them I was. It turns out you have to send the phone to a different location if you were on a jump program. I didn't notice that before I sent the phone back with the label they gave me. This time I said that they should still have the phone at the place where phones arrive if they are not from a demand program.

The CS rep took me off collections again and said they would look for it. Note that I was in the process of moving when i switched phones and i lost the original tracking label. 

Anyway I just got another collection notice and I am asking for help with how to find this phone. T-mobile has it they just aren't looking for it.