First National Bank
FNB are money hungry

I have had the issue of money going off my account too late and then leaving my account in a negative for a while now. I spoke to a consultant who told me that transactions done through swiping sometimes take longer as FNB waits for some kind of authorization slip/code before the transaction finally goes through.
On my online banking i can see my balance (x), my available balance (y) and then money waiting for this authorization (z); So (X)-(Z) = (Y)

If Z is reserved for transactions why do those transactions go of and get deducted from the available balance? Does this mean the transaction goes through twice as money is reserved to pay for it separate from the available balance. Also how in the world do big store's transactions only go through a week after the purchase was made? Don't these people bank their speedpoint machines on a regular basis? Or do they really only do it once a week? Because i find that very hard to believe.
As a result of this, my account is once again in a negative and FNB proceeded to penalize me by a incidental credit fee?

I need clear answers on this, This bank is only costing me money now. Is that the nature of your business?