Unauthorized debit orders

I went to Nedbank Lephalale mall to reverse the debit order that has been going through on my account since August 2017. I was not aware of the debit order because the bank notification service was not notifying me because of the amount.The bank told me they will only be able to reverse one debit order because the other ones were older than 40 days and they would charge me 50 Rand for a stop payment .I consider that a **************** ,my money is not safe in the bank, surely they know about these unauthorized debit orders,FNB is able to reverse as far back as possible ,why can't they!