Magtape Unpaid when funds available are clearly shown in account

I logged a complaint on 11 September, querying why a few of my Debit Orders went (Magtape) unpaid when I very clearly, as shown on my transactions, had more than sufficient funds in my account. Someone from their Personal and Private Service Recovery department sent a reply showing two transactions and then claiming the account in excess, NO further explanation. Not even reading my query to understand! I rep**** on 13 September with a clear screenshot of the account showing funds available and the unpaid debit orders while STILL showing funds available to which I asked for an explanation. No reply from, IRONICALLY, the Service Recovery team. I followed up for an explanation on the 16th again, with absolutely no success and this morning the 20th; AGAIN. I have bank charges that I now have to cover when in actual FACT, there was no reason for the debit order to go unpaid. If I was misunderstanding something, I would think FNB regarded their clients with enough respect to provide an explanation.