Overcharging

Overcharging their clients. I have nedbank account. They have a tendency to overcharge me. I bought something at the supermarket on the 15th by than I had a positive balance, and the soon as I swi my card the money is deducted. Now on the 18th there is a hon fee if R90 because I have swiped my card at the supermarket. This is not the first time and I wonder how do they work to rob their clients so much money. No single day where I swiped my card with negative balance, but because of their charges I ended up with negative balance. I have 3x R 90 charged. Nedbank is a nightmare I promise you