Cancel my contract!

I called MTN last month to cancel my contract with them and was advised to call closer to the 12th to do so after attempting to retain me. I called again on the 5th of October to cancel and could not hold on any longer after 30 mins for someone to take my call. I sent an email to *** requesting that they cancel my policy and to date have not received any acknowledgment of my complaint. This morning I have been credited again which in turn means my bank account will be debited this month again, this after I specifically in my email said they must not debit my account this month and going forward. I expect someone to cancel my contract as I would like to move to prepaid (and subsequently change providers) and reverse the credit on my account as I do not want a debit order going off this month!