Failure to assist me with ***** on my account

I am the treasurer of a trust for a school for unprivileged children and have noted over the past few months that a number of ********** debit orders have been created on our account. I have tried to stop these unauthorised transactions but FNB will only assist to reverse the individual debit order and not stop the debit order completely. They then charge R15.00 per reversal. This is unacceptable. This money is used to fund a charitable trust and our account has clearly been breached. Yet FNB fails to investigate and prevent any more of these ******** transactions from occurring. The members of the ***** unit just pass me from one member to another because they don't know how to solve my problem.