Banking charges with fnb

Fnb has a tendency of banking more than it reserves. I tried contacting them via secure chat and via queries with private and personal queries. They said it is due to the fact that the merchant does not bank immediately so meaning as FNB clients we have to wait for the merchants to bank in order to spend our money. When a transaction is made they reserve the amount yet when they bank they want to bank more. I would not recommend anyone to bank with them they don't have a transparent policy. I will definitely be cancelling any subscriptions with them and migrating my salary.