Unpaid Items Ripoff

This is supposed to be a zero rating. FNB is the biggest *****. I've been charged for unpaid items due to the merchant doing their banking late. At the time of the transaction, I had funds in my account and got the relevant notification that the funds had left my account after the purchase, it just doesn't make sense. How many millions do they take away from their customers this way. FNB please explain to us customers how is it our fault that the merchant does their banking late and you send us the notification that the funds have been set aside for that specific transaction but we still get charged honoring fees