poor and *********** staff

Yesterday I bought 1kg Onions peeled which was on special and was overcharged. Upon realizing it was overcharged I returned to the till and show the cashier she went to the fridge and called for supervisor. The supervisor was so rude and loud telling me those were just Onions. I then told her she must not give me a lecture because those are peeled onions and the big tag on the onion is priced and was to pay as per their sale leaflet. I asked her name and she refused I told her to call the manager as I will report her rude and *********** expression and she refused. A gentleman came in front I asked for the name he said her name was Christinah left very disappointed at that bad, rude behaviour and how you would keep such staff in the frontline.