Debit order contract date has changed without my permission or my signature

Good day, I have a contract with telkom payment is signed to be debited on last day of the month doesn't matter even if it's weekend the instalment has to be debited last day of the month, I see in August they tried to debit on the 30th Aug which is not what I have signed for. Its not fair at all because they are no longer following my contract???? I need answers Account Fwd: Telkom Invoices and Statements - ***