WRONG AMOUNT DEBITED AGAIN!!!

My husband and I have a contract with Vodacom for R60 per month for two handsets which consists of R100 airtime and free bis for a period of 24 months for each handset.This was offered to us as our older contract was coming to an end.I am about 9 months into the contract.I have had a problem each and every month without fail from Vodacom.We found out that the invoice that was submitted was incorrect for one of the handsets at the beginning of the contract and that the there is no way that the accounts department could rectify the problem.We had to call in every month and explain everything to the consultant and it took days for it to be activated again.There was an increase in the amount that we had to pay and the contract is gone up to R80 with R110 airtime and free bis per handset.On one occasion the consultant charged me for the free bis and i called in and complained and it was credited back to our account.Once again Vodacom debits the wrong amount from our account.The total for the contract is R160 and we were debited today for R219.If we did not have funds in the account we would be liable to pay bank charges if the debit bounced.WORSE CUSTOMER SERVICE PROVIDER! DISSAPOINTING