Vodacom forcing you to keep their contract even though you have requested a cancellation on their contract and giving reference numbers that don't work

I'm not happy with Vodacom I have logged more than 4 requests with them for contract cancellation since January but they are not canceling the contract. Every time I call to cancel they say the contract has been canceled and give me a reference number and then month end they charge and give me data even though I have specified that I no longer need the contract since it has ended. And then again their reference numbers don't work when you speak to their consultants meaning they give a reference number knowing very well that it won't work.