Customers pay the price they see on labels

Popped in exact boulders today 21 October 2015 at about 12:15 pm as my friend wanted to buy something. as I was looking I saw a set of three dresses for R170 (sizes 7-8) that were on a hanged on a hanger designed for a set of three dresses. I then decided to buy that set. When I got to the till I was told that someone had erroneously used a wrong hanger as the dresses were meant to be a set of two and the other was sold separately for R130. No dress was hanged on top of each other, for me know that it was a mistake, all were on their designated space on the hanger. How does the store use false advertising? No one was interested in solving mu issue I was told that if I don't want to pay for the other dress i must leave the dresses. As far as I am aware, the client pays what they see on the label. I don't work at the store, I don't set prices or label clothes, so I expect to pay what I see on the label.