Struggling to come out of an MTN Cellphone Contract :(

My cellphone contract with MTN ended in August, I have since then been trying to get MTN to cancel/stop this contract because now they are debiting my account despite the contract coming to an end. MTN has been giving me a run around. I was told to phone and email the retentions department but have found no joy. I have also been inboxing their Facebook page and all I am told is that we are escalating and awaiting feedback. A month and countless reference numbers later I am still stuck with this contract. What does one then do in such a situation? I am soooooo frustrated, I don't even know what to do anymore. MTN please do better.