No refund check yet

When I called about a promised credit after so many contacts, finally a man applied the promised credit and processed the refund check because I don't have an active service anymore. However, I haven't received the check to my address yet. I called but they said there's no refund check record. Now, my negative balance on my account has changed with no reason since the day when I confirmed my refund amount.

The agent on the calling even said my account is in a collection status. The man who processed the refund check confirmed my account is clear and not in a collection staus at all. 

Please just mail me my promised refund check to my address that I told the man.

Please stop sending me back and forth between different departments.