Vodacom refusing to cancel contract

I am struggling to cancel a contract since September. Vodacom absolutely refuses to process the cancelation. Every time I call I spend over 45 minutes on the phone and the agent says in the end its processed and I will get confirmation, but I never do, thus I call again and again, each time the new agent has no view of my previous call and it starts again. How can I cancel this contract please vodacom?? I get no ref or confirmation post call but I do have the records of the sms I automatically received most times I managed to get through. I've called on 8/9, 29/09, 13/10, 14/10, 02/11, 8/11. These are the times I received sms's. I didn't receive sms's every time I called. This morning I spoke to Mohammed in the cancellation department, that's the closest thing I have to a reference of this cancellation logged. Please help?