No response from Cell C

I had a Cell C contract. I cancelled it 5 November 2015 one month before it had to be renewed and they said my contract will not carry on. I was billed at the end of December 2015 i enquired it and they said it was billed for the last time. End of January 2016 i was billed again and i reversed the debit order because they did not stop it. Now today 20/01/2016 i was billed again. When i turned on the spare phone the sim card was deactivated and they said my minutes that was build up will only expire 3 months after the contract was cancelled. They make promises that they can't keep and they still bill me after my contract was cancelled. And now i can't phone them from land line because i need to phone from the number and the sim card is deactivated. Please this is pathetic. I need assistance in resolving this. Now i have to take off work to go to the bank pay R35 to reverse the debit order and this will now be the second time. I can't do this every month because they did not cancel my contract from their side.