unacceptable price increase at shelf

I went to clicks to buy a new iron. I went to the shelf, picked up my pink Kambrook 2600W iron & was on my way to the till when one of the clicks ladies approached the shelf, looked at a list of price tags in her hand, took out the price of the exact iron I was holding&told me it has JUST gone up. When I took it off the shelf it was still R279 but now suddenly I had to pay R329. I was unhappy about it &told her that I'm not paying more for it. She said she'll be right back, took the prices with her& left. She came back& told me it has definitely gone up- I had to pay R329. I said no &took a different one. A 2200W blue Kambrook iron. She said she will check, but it has also gone up. She then agreed that I can still pay R219 as on shelf, but took out the price afterwards& it is now R279. What really upsets me is the fact that I wanted the 2600W iron& they can not just decide to change the price when someone takes a product off the shelf in 5minutes' time. Why could she give that one to me for the price on the shelf but not the one that I was holding when she suddenly decided to change the price?? Prices should NOT increase the minute one takes it off the shelf. Especially old stock