c fibre *******. refusing to cancel my contract

I have been trying to cancel my c fibre account for minths. they keep invoicing me instead of cancelling the line as requested. I have numerous reference numbers but cell c refuses to cancel my contract as requested . all my nails go unanswered but they are quick to send me invoices for something o am not using. when I call the call centre no-one can add is. they assure me the cancellation department are working on it and that I won't be charged further but here we are with a new invoice received again. please cancel my contract and stop *****ing my money