Early deduction of loan repayments

Standard Bank is once again deducting their loan re-payments earlier than the agreed upon date in December. I had the same issue last year and numerous emails and phone calls fell on deaf ears. I signed a contract to deduct the re-payment on the 25th of each month and I expect Standard Bank to stick to this agreement just like they expect me to pay the account every month. They basically ignored my complaints last year, so I'm not expecting anything different. I am definitely moving all my accounts to another bank.