Theft from Pensioner - MTN not actioning request to cancel service

I have been trying for months (since Aug) to cancel my 2 MTN contracts - numerous attempts, numerous agents hanging up on me or providing false information. Calling the 135 is useless as the agents terminate the call if they cannot retain the customer. When asking the call agent for their name and reference they sigh and end the call. As a pensioner, I can no longer afford these services and have followed due diligence to end the service properly. I have tried to keep my part of the transaction clear, but am currently being given the cold shoulder and run around by a big corporate bully i.e. MTN. The service from MTN is appalling! Stop taking my money when I have asked numerous times to cancel. This is on the brink of theft from a pensioner! Disgusting MTN