ABSA REFUSING TO REFUND AN OVERPAYMENT

Over paid a secondary bond account with Absa and they are refusing to refund the credit amount. Have had 5 emails with them all of which seem to be automated RESPONSES. The branch says that they can only repay amounts of R1000 and over. So that didn't work. The amount in question is minor but the moral of this is that if I owed ABSA even a penny, they would add interest till and expect me to pay in full. Why not extend the same courtesy to their customers?? Also, HOW MANY MINOR AMOUNTS DO BANKS KEEP FROM THEIR CUSTOMERS ANNUALLY AND HOW MUCH DO THESE AMOUNTS AMOUNT TO ANNUALLY. MOST DISSATISFIED AND TAKING THIS TO THE BANKING REGULATOR.