False advertising

I went to Game (Woodlands Boulevard) yesterday to purchase headphones. There was a shelf of Volkano Rhythum Series headphones "on promotion". The price on the shelf was R119.00 When I took the headphones to the till, they came up as R159.00. I explained to the cashier that they were on promotion and was asked to show a lady where they said that. I took her back to the shelf, and showed her the only price on the whole shelf (R119.00) and the big "On Promotion" sign. She says "ah, that's only for the Pink ones" and walks away. There were white, blue and pink headphones of the same make and model, on the same shelf. With only one price. How is a shopper supposed to know which colour are on special or not. USELESS.