over charged account and terrible customer service

After purchasing a contract from an in store. I started having problems with vodacom and their billing. They have debt my account 4 times in 1 month totally to R700 which is more than the account itself. I called up on numerous times to solve the issue spoke to Musa , Nomusa, sandile etc etc etc. All i was told that problem was excalatored and i would receive a call in 24 hours which up to now has not come. I have stopped the bank from paying any more debt orders to vodacom and will not pay them as they have not disclosed accurate information regarding the product i purchased and thier customer services does not have utmost good faith as all their agent have not been trained to handle problems as all they do is pass the buck on to the next which leaves the problem unsolved.