Pathetic after sales service

I have cancelled my DSTV almost 2 years ago. I called them and informed them i am going to cancel my subscription. They gave me an amount to pay which i did. And my subscription was terminated. Now i kept on receiving phone calls from them i own them money. With every call i ask them for the proof that i still own them but they refuse to provide proof. They are busy harashing me by their phone calls. This is pathetic service from them to demand mo ey but cant send proof. DSTV STOP HARASSING ME PLEASE. Do your job as ypu supose ro do.