fnb feels and looks like they are *****ing

i have been a customer of fnb for a long time i even revered i talk very one that i talked to to them.... but now after a couple of very hard years i can start to build my self up..... but fnb is making it very difficult..... they have this thing of when you swipe that your money goes from your available balance to balance..... lately a few days after pay day that balance disappears... my available goes to minus..... after 3days of phoning talking to deferent consultants each with a different story of why its happening me pleading to reveres the charges because my last money for the month is being paid in thy didn't and took it all..... the don't contact you explaining their reasons why..... i had enough now can't go on like this..... at the end of the month I'm changing banks it feels and looks like steel to me