Return of Equipment

I was with Directv.  Although the ad said that I was guaranteed a price of $19.95 for a year, this did not occur.  Somewhere between 3 and 6 months my bill went to $79.95. I called around found this was still an okay price for the services I received, I did call the company and complained but nothing was done.  Basically was told if I wanted to continue my service, pay the bill.  I did however find other ¨deals¨ out there but I had a contract with them, why add more to my cost?  I discontinued my service as soon as I could and was instructed to return the equipment.  I had done as I had been initially told and kept the original boxes, with return labels and mailed them back only a day after stopping service.  About 6 months later, I received a box from Directv, with return labels.  I called the help center and was told that they got thousands of boxes returned each day and ¨yes¨ although I had returned it months prior, it most likely hadn´t been processed yet.  I checked my credit report not much later and there was a bill in collections for these ¨unreturned¨ boxes.  Now why would anyone want this equipment?  It´s not like I can use it and I had already gotten with a company I loved.  What can I do to get this off my credit report?  Directv is absolutely no help.  Does anyone have any ideas?