******** debit of account

We are approaching August now and my contract was due to end in May. I have phoned MTN numerous times to cancel the contract, and still it has not been done. I requested in April, that my contract be cancelled and converted to prepaid, it was not done, i phoned again in May and requested the same, it was not done. I then noticed that they were still debiting my account for an amount that was completely different to my normal debit order which should have been cancelled anyway. They have continued to debit my account and have not responded to my email I sent upon receiving a statement from them for an account that was supposed to be cancelled in May. The second lady i spoke to assured me that the call was recorded, so MTN is welcome to check their call history and trace my call in which I requested the contract to be cancelled. I had trouble with MTN when I took this contract and i am having trouble cancelling it. I will never take up another contract with MTN again. I also need them to stop debiting my account.