Price discrepancy and poor attitude

I noted a discrepancy on the prices of identical items. I was told by the shop assistant that it will be resolved at the till. When I got to the till they were extremely unhelpful and had a bad attitude. I asked for the manager and my request was ignored. When I checked the price of the item online it was clear that the one item was incorrectly priced. This was even presented to the shop assistant. To further validate that this was an issue I have obtained pictures of the online pricing as well as the price on each of the items. It is shocking how they could not see the issue nor were willing to resolve it.