Vodacom Finance Dept - Serious System Error

For the second month in a row Vodacom has debited my account successfully and then sent me an sms telling me to call their finance department because they were not able to process my debit order- last month I was told it was a system error and the agent had sorted it - same thing happened this evening- please call me with an explanation and what will be done so that it doesn’t happen again. KR