Item paid no funds

I have an account at fnb without an overdraft. I have recently made purchases on fnb online and the transactions were baked late. becuase of this i recieved two #ITEM PAID NO FUNDS but the money was reserved on my account and should not have been an issue and I realised other people have the same issue and i have talked to consultants on the fnb app all they do is give me a generic response and end the conversation without even checking the details. the money was in my account at the time ofthe purchase and should have been resrved and the fact that you charged me money for #ITEM PAID NO FUNDS is just ridiculous