Bad pricing

I went to foshini and saw nails I asked the one lady whats the price on the nails she went to check it for me she said its R129,95 so I took 2 sets of the kiss Nails. Then I wanted to pay fot it the lady said the one set is R 129,95 and the other one is R149,95 so they called the manager also so she also said no the other one is R149,95 but I got another one also only the size was different size of nails with the same price on it R129,95 but they still didn't want to give it for me. Both of the personal that helped me wasn't very friendly and thr fault was on their side with pricing how can they price something a certain price and then ask like R20 extra.