FNB debits money without permission

I'm terribly disappointed by how FNB has tested me. On 15 December they made a pre-deduction on my account without my permission. My agreement is clear to them that my account be debited on the 1st of every month...this is on a contract I signed with them. Now the excuse I got is that I got paid my salary early and I made it clear to them that I use my money for many other personal things and make sure I have money available for their debit order. The arrogance and attitude I was given when I enquired about this is beyong appalling. The agent told me that if I have a problem I must go ask my employer to give them evidence that I was not paid before payday. And that was not the point, my problem is the fact that FNB takes it upon themselves to debit money from my account before the due date without my permission. I told them that the Ombudsman was in the media on 18 December confirming that this behaviour is not acceptable, they ignored me, showing clearly that they are above the Ombudsman, they do as they please with customers money. I am very very upset, after banking with FNB for more than 20 years this is the treatment I get. I feel VERY disrespected