Vodacom incorrect billing and debit order

We have been dealing with a billing issue with vodacom for the last 6 months. You call speak numerous consultants. We brought this issues to their attention. Each call resulted in informing us the issue will be sorted with the next bill run. We received an email stating our account is in credit yesterday 2nd May. We now have been debited 5k on the 3rd May. You ask to speak to manages no joy. You ask to be connected to the CEO's they are unable to do so.