VODACOM'S DEBIT ORDER SYSTEM SUCKS

Who gives Vodacom the right to deduct a debit order earlier than the last day if the month as per contract? That's tantamount to faud! As a result the debit order was returned and now I will be cut off continuously ('by the system'- according to their agents), even though I paid the account in full afterwards. This is exactly what happened last month and it's unacceptable!