Unfair charges and bad service

Extremely disappointed in FNB as a bank and with their customer service who seems to know absolutely nothing. Me and my wife have been banking with FNB for years and it seems that now I have to change banks. I had previously canceled and stopped a debit order with fnb. However when the service provider tried to double debit me, the debit order went through even though there was no funds in the account. FNB had advised me that if the amount changes,the debit order will still go through. Now FNB cheque account has a very confusing and stupid way of operating. When u swipe ur card money comes out from available amount but it's doesn't come out from your balance until the business where you made a purchase does their banking. This means that all the payments I had made went off from available funds and not balance. Because of the debit order went through my account was in a negative so when the businesses did their banking fnb charged me an additional R1590 in charges for honoring payments. When I had the debit order reversed back into my account, FNB refused to reverse my charges as they say its valid. What is unfair is that when I made purchases I had money in my account but because it only came out of available funds and not my balance,I have to now pay R1590 in charges for something that is not my fault. FNB is really ridiculous and on top of that the people at the branch say they can't help I must contact the guys using the app who doesn't seem to even understand how their own systems work because I had to explain everything to them. At the end of the day,these charges were not my fault in the first place amd should be refunded to me. Me and my wife will be moving to a new bank very soon and we will be taking our business bank account with us.