Wrong Pricing / BAd Attitude

HI, I went to our local Spar yesterday as I always do to purchase some last minute items for my daughter for school. After paying for my stuff, I realised that I was overcharged for X3 Toilet Rolls - R5.49 on the shelf and R5.99 at the till, as well as Par Germex Hand soap, R21,00 on the self and R23.49 at the till. When I said to the lady that I was overcharged, we walked to the isle and her initial reaction was there has been a price increase that's why the price is different. She then returned and said that although the shelf price tag's description and positioning matched the Item that I had purchase, she said sorry the barcode is different. I then asked her where was the price tag for the Item that I had in my hand...her response was there isnt one. I then asked her where is the item that was R21.00 cos that's what I want, she then responded very abruptly -\IT'S OUT OF STOCK