Wrong prices on goods

I went to their store on the 23rd of December 2015 and the Diablo 3 PS4 games were priced at R299 on the rack. When i wanted to buy the game, the lady said the special ended and she could not give the game at that price. I told her it was their mistake and they should take responsibility for it, not me. She insisted that the special already ended on the 16th of December. I asked to see the manager and she claimed that she is the manager. Then I told her that as the manager she is responsible for checking that the prices on the games are correct and thus I insist on getting it at that price. She refused to talk to me and started helping other clients. I asked her to help me and she said that she has other clients to help, which I feel is very rude because I am a loyal client to this specific branch. I did not price the games wrong, they did, and they must pay for the mistake then, not me. Very dissatisfied with the service.