DirecTV AT&T/DirecTV Both AT&T and DirecTV billing me for same service Nationwide

I had internet with AT&T and TV with DirecTV. At one time they were billing me separately. Then when the companies merged they started sending me a combined bill.  I disconnected my internet (there was no contract) but continued the Direct TV until my contract with them expired in May 2017. I continued to get a "combined" bill from AT&T.

When I cancelled my DirecTV in May 2017 they continued to provide me service after I requested it be cancelled. Then I had to call them three times to get shipping materials to return my box, which I finally got. However, I started getting billed for DirecTV from both DTV and AT&T!

I returned my DTV box and have the receipts to prove it. However, both AT&T and DirecTV billed me for two additional months of DirecTV service even after I had returned the box. I tried to buy a car this past weekend and find both AT&T and DirecTV have placed collection notices on my credit report. I cannot access my account on either web site but I recently got a bill for the so-called balance AND the box (which I returned) from DirecTV. Now I have to go through the hassle of disputing these bills and trying to get them corrected. So both AT&T and DirecTV are saying I have a balance of three months service (two separate amounts) and DTV claims I owe them for the box also!