Cell C still Billing on a cancelled contract

After being a client of Cell C for 2 years, I have never experienced such bad service from them. I had a month to month fibre contract which I cancelled before leaving the premises I was a tenant and.... 6 months after, Dozens of times trying to get this matter resolved I am still being billed. The bill has accumulated to above R9k. What really ****ed me off today is that I received a call from their credit controller ( T Maifala - email ********** or whatever his position is and he was the most rude person who portrays Cell C as they are. I tried explaining the situation to him and he starts calling me "confused" and funny names before he hung up his phone on me. I even sent him email trails of my past communications with Cell C regarding the same "account". I just want this matter to be resolved ASAP as it is wasting my time.