****er charges for unpaid debit orders

I tried to stop debit orders on my business account because I had insufficient funds. FNB has now a R200 limit which can be stopped manually by the customer, any amount above that needs to be done by the FNB consultant and you get charged R20 per debit order. You also get told that this service is not guaranteed that the debit order will be stopped. On the due that all the debit orders went through and was charged R185 per unpaid debit order. Just checked my bank statement today and discovered that FNB charged my business account just over R5000 for these unpaid debit orders and there was nothing which I could do to minimize the damage. What is more frustrating is the people who were running the debit orders on my account managed to re-run these once again and was charged twice in the amount of R185 per unpaid debit order during the same month.