Holding account on minus for more than 24hours

FNB Private Clients instead of dishonoring a debit order on the 20th due to insufficient funds, they hold it on minus till the 24th so that they can keep accruing charges which are now at R176. When you need them to that while you waiting for funds, they decline. And now they want be selective to what they think is important. If there is no funds, just decline and take your once off fee. Now every fund which gets paid I can't access it because they want make favours for service provider which I didn't have a debit mandate with them.