Cell C's *********ing of payment

I have had enough of trying to deal with Cell C. i called in late October last year to move my installation address, due to their atrocious turnaround time in just responding to my query i requested cancellation of my account at the end of October beginning of November. I paid for November as I understand there is a notice period on a cancellation of any account, however my account was only closed at the end of December due to the cancellation department only looking at my requests weeks after I logged them. Now I have their collections department trying to force me into paying for the month of December. All of this whilst not receiving any service from Cell C as they couldn't even assist in the moving of my installation address. I no longer have any faith in the ethics of how Cell C does business nor do I ever want to have further dealings of them in the future. Now all my escalations of them get closed before any investigating and they are unwilling to assist me on this.