Pick n Pay Randridge Mall - Incorrect Prices Charged, holding customers liable

PICK N PAY RANDRIDGE MALL - I was over charged, so I went for a refund. After first standing there for about 15 mins whilst they figuring it out. They ask me for my details, of which I said no.The next cashier whilst busy with her customer, tells me they can't help me without. I tried to explain the inconvenience they had caused me by overcharging me. Though she was not interested, she wanted the details. We ended up going back and forth shouting at each other in the store. I was high irriate when I left the shop because they had overcharged me, because she was me accountable for the incorrect prices of PNP. What was she almost forcing me for my details.