First national Collection Bureau

I recieved a call from these people today stating that I have an old debt with Direct TV from 2008. I have NEVER had Direct TV and informed them of this. The agent on the phone said "These calls will continue until this debt is paid". I hung up with them and called Direct TV who states they have no account under my name. When I called First National Collection Bureau back I asked them for a copy of the bill at which point I was transfered to another person who said that because I had already been sent letters notifying me of this debt (which I have never recieved) that they would not send me a copy of the bill.

I guess they think I'm going to pay them money for something I have no clue about. I've sent out my letters of validation and cease and desist but does anyone know if there is anything that can be done about them refusing to send me a copy of this so called debt?