Fnb charges for services as it was their mistake

I pay pay flex from my fnb account as there was money available as my salary was paid in. To my surprise on the 14 October 2021 FNB CHARGE ME R270 FOR FUNDS NOT AVAILABLE. BECAUSE OF R270 SOME OF MY DEBIT ORDERS WILL NOT GO OFF AND I WILL BE AGAIN CHARGED FOR IT. FNB FEES IS OUTRAGES AND RIDICULOUS AS IT WAS NOT MY MISTAKE AS I DID HAVE MONEY AVAILABLE