FNB and unpaid items fees after transactions were concluded when money was still available

I have been charged for a transaction I made a week before when I had money in my account. I bought something for R98, which had gone off my account when I still had money in my account. However, FNB charged me R180 for the same transaction as if it was an unpaid transaction. Today I was charged R180 again for something similar, after I saw a message that my account is overdrawn by R7.99!!!

Why is it that purchases go off our accounts but are kept as pending when you've deducted money from the sane account for that purchase?

I picked up that this happens a lot with FNB. There's a lot of people complaining of the same issue, as far back as 2017. Calling the supposedly premier banker is always a waste of time! I refuse to be treated like this when I've been with this bank since 2010!