NO HELP FROM CELL C TO CANCEL CONTRACT

I've been trying to cancel my Cell C contract for how long already and everytime nothing gets cancelled and my account gets billed every month even though I don't have my cell c simcard for more then 2 years already. I contact their customer service and everytime they want to transfer me to their retention department the line is dead. Before the consultant transfers you they warn you beforehand should the line get cut you must contact the 084 135 number option 2, but the line never works. All I want is to cancel my account immediately. This is the worst service ever!!!