MTN refuses to cancel contract

I have had no joy with my MTN contract in regards to cancellation. I called in January 2018 to cancel and was told to call in Feb when my contract reached the end of the term, I called then 01/03/2018 to cancel and was told that there was an oustanding amount due to pay in order to cancel falling within the 24 month period which I have agreed to pay but advised the consultant to cancel this contract immediately as I have called already and they should note it. I paid this amount oustanding and now I am notified that I owe more money as my contract was never cancelled and they are still continuing with sending me data and free minutes that I dont want. I will not pay this money as I requested cancelleation and feel that MTN is forcing me to continue with a contract. I will be forever owing money and stuck in this contract I dont want. need urgent assistance with stopping this contract as I will not pay for something that I requested to stop.