Difference in pricing very bad at PNP HYPER OTTERY

PNP I’m Ottery was always my go to store but recently, I have discovered that their pricing is not right. Before school started, I bought a pencil bag which was priced as R79,99. When I got to the till and it was scanned, it scanned as R149,99. Today I went to buy eggs, on the shelf the price was R49,99 but at the till, it scanned R64,99. On both occasions, I was told that the prices were incorrect but I had to pay the price that was scanned. Doesn’t PNP have a policy that you pay the price on the shelf because I advised the staff member, by right I was supposed to pay the price on display but she disagreed and I ended up leaving the items. This is very unprofessional and it seems to be happening quite a bit. They should fix their pricing and if they cannot do that, the customer should pay what is being displayed because the reason you take the item is because of the price being displayed. Really disgusting and not one apology from either of the staff members.