Unwilling to assist with ***** on my account

Since April this year I have been receiving bills from MTN and my account was debited. I dont use MTN ever. So I contacted them and they said I have 2 3 year contracts taken out with them!! Say what?! So they told me what paperwork to submit to say there was ***** on my name and bank account, and to this day, they have done NOTHING about it. They keep phoning and harassing, but they are NOT my service provider, and i have NEVER taken out a contract with them. And I proved that with an affadavit, and yet, they cant be bothered to assist me. Absolutely not good enough.