Chancer cashier/ not enough cashiers Pep

I was at Pep stores Alberton city yesterday. And again on month end and black friday only two cashiers. My back was so painful standing in the queue forever. And then the cashier who assisted me (Avile Mavis) wanted me to pay more money than I had to pay. I bought some stuff on special and usually I count my things before I get to the till. She said I have to pay R587. I told her it was not the correct amount. Then suddenly she said: Oh, I didn't finalize the amount yet. The amount I had to pay was R408. If I kept quiet she would have taken RR179 from me. She took a chance on me but luckily I was prepared.