Payment for installation of alarm

I don't understand why i'm getting statements and phone calls that i'm awing ADT for installation of my alarm ,while I did payed before the installation was done .

I did emailed the consultant prof of payment, and he acknowledged revived the prof of payment and I also emailed it to account DEPT for the 3rd time but still reciving call of non payment everytime they say they will look to that, but come the following month I recive phone call of non payment . my payment that was done on the 20th February. Now is May but ADT keep on saying im awing them .