Contract not cancelled 7 months late

I have called the call centre 5 times and been promised every time that within 24 hours my contract will be cancelled. 7 months later my line is still not cancelled. I spoke with a call centre agent on Friday who took my details and told me a manager would contact me back. It is now Wednesday and I still have not received the call. I have not used this line since April and as long as I continue to pay nothing will be done. I absolutely refuse to allow anymore deductions and extra fees that are being charged. It was great service when taking out the contract and I honored my two year agreement. I had every intention of taking a new contract when I was on my own again as we have a fixed internet line currently but this experience has made me never want to deal with Telkom ever again. I have proof of all the people of who I forwarded my cancellation form to. The service is absolutely pathetic that I have received.