Wrong pricing and bad customer service

Went to Game jubilee mall today to purchase a Volkano GPS watch for kids, it was priced R399 and when I got to the till it was rung as R799. I asked to purchase it for R399 because that was the price I saw but they didn't help me and I asked for the manager and the manager did not come...I am bored by the service because I wanted it to be my daughter's present as it is her birthday today. And it is not the 1st time I encounter a pricing problem with them.