Non Authorised debit orders

Debit order was deducted 4 times in one month - actually within a period of 2 weeks. After the first wrong debit order numerous calls was made to the call centre to rectify NEDBANK's mistake, then you get told it can take up to 48hours, after they do deductions immediately - without your consent. The 1st debit order went off on the 12 paid back on the 14th. Again on the 21st - DOUBLE, paid back on the 23rd,(only the one that was wrongfully debited- as they did get the instalment on this day) the same day on the 23rd as they paid it back they debited it again, after phoning again, no money was paid back and the same debit order was deducted again on the 24th. On the 21st Dec I visited the Branch to rectify this, was with the Branch Manager. On the 23rd I was promised that no debit orders was loaded until January. but after the telephone conversation on the same day and the next day they deducted it again, every time when you phone NEDBANK to rectify a WRONGFULLY debited debit order they check if you owe them money, which is not the case and every time promise that it wont happen again, they got their debit order on the 21st. and now they keep on debiting my account, STOP! Plse Help!