Bad service Shoprite Paarl Western Cape

Hi. Yesterday me and my sister went grocery shopping at Shoprite Paarl Lady Grey Street. We got at the pay point and paid for the groceries and walked out. As we walked out I told my sister "let me just check if my till-slip is correct". I then saw something really shocking on my slip and said ti her wait lets go back. We went back into the shop to the same till where we were and I told the cashier that on the slip it shows she scanned an item twice which I only had bought one item. I asked her to look in the trolley to see for herself than the other person that helped the cashier packing the groceries said that she saw two items when she packed the bags. Me and my sister said no we didnt buy two of that because where is the other item. The other lady insisted that she saw two items while packing the bags. I then asked them why would I have come back immediately if it wasnt true. So the cashier called the manager and she told the manager that she scanned one item twice. So the manager then said they going to give the money back. So I went with the manager to another till-point where another lady helped me . I had to write down my Name and other details. She left for a short while and I stood there waiting for my money. She got back and gave me my till-slip back. Then I asked her where is the money that I must get back. She then said " I already gave it to you" . I told her that she didnt give me anything. Then she said again "I did give you the money" I said oh my word dont make me more furious now. Right next to me was another customer and I asked the customer if she saw the that cashier gave me the money. Then the customer said no she didnt see anything. So the cashier left to go fetch my refund money. I was so angry. I think such behaviour is unfair towards we as customers. They didnt even apologise for the mistake they did.