FNB ripping me off daily for a ****en R50 transaction they decided to deduct days later???

This is getting ridiculous now. I did a transaction of R50on the 15th when I still had money in the account, FNB went and decided to only deduct it on the 19th which put me in a overdraft. Now I am being charged daily on this transaction. this is a total *******. They ****ming us out of our own money, Why ****en wait till all the monthly charges are being deducted to deduct transactions I did days before. Every time I swiped the balance decreased but they still say the transactions did not go through.

Is this now the new way of making money since they are losing clients????