Vodacom billing incorrect - no response

I have been trying to get Vodacom to reverse an incorrectly charged amount from my account for more than two months now. Everytime I call them they agree that this is incorrect, after a lengthy explaination to a negetive call center attendant. Then they log a dispute and promise to call me. I have called them several times now, same promise each time and i am still waiting. My line has been blocked and I am paying my monthly instalment for nothing. Vodacom doesn't care.