Contact Cancellation done incorrectly

I called Cell C 143 contract retention department on 22 November 2017 - to provide 30 days notice so that my contact is to be canceled on 22 December 2017. My 24-month contact was due to end on 20 December 2017. I spoke to Maxi-million (agent) confirming my that my contract will end 22 December 2017, whereby my cell c sim will then be on prepaid basis. He stated that my last debit order will be 31 January 2018. First issue, last debit order should be on 31 December 2017. Second issue, my cell c contract was cancelled on 22 November 2017. My SIM is now on prepaid, after specifically confirming date to be cancelled was to be 22 December 2017. I called 143 again, Max confirmed he has made a mistake but I could not get hold of a supervisor to confirm how this will be corrected. This simple request has now taken 3 hours of my day to try and resolve. I also called ********** 007 as given on sms reference. They again put me through to 143 contract retention department. This is really frustrating!!!