How is a person supposed to get an MTN contract cancelled???

I have called in about 6 times trying to cancel my MTN contract. I called for the first time 2 months prior to the end of the contract. I was then told by a call centre agent that I need to call 1 month prior to the end of the contract to give 1 months notice. I then called 1 month prior to the end of the contract and was told that their system doesn't allow them to schedule a cancellation and that I need to call on the day the contract ends which was the 10th of September... a Sunday which the contracts department would not be open. I then called in on Friday the 8th of September so ensure they would receive the instruction on time... the contract is STILL not cancelled... I have even been to the MTN store in Menlyn Park where I was told they cannot do a cancellation in store. I have now been waiting on the line for your retentions department for 40 minutes... What must a person do to cancel an MTN contract??? Your service is beyond pathetic...