Cancelled MTN contract is still billed.

I took out cellphone contract with MTN over the phone which was due to expire end of October 2015. I called in on the 5th of October to cancel my contract and was advised that a request has been sent and the process will take 30 working days to be completed.Ever since I have called in more than 15 times to follow up on a the cancellation. I was billed on the 28th of December 2015. I find the service to be appalling as every time I call in, I'm assured that my contract has been cancelled and NO OTHER debits will be done on my account. This will cause my name to be black listed and I will not stand for that. I have NEVER skipped any payments and this is the service I get? I will never have a MTN account and I want this matter to be sorted out by a manager calling me and confirming that all is sorted, no outstanding amounts and no contact. <br> <br> I am very dissapointed that I trusted that the issue wil be sorted ot. My contract number has now been migrated to pay as you.