Bad customer service

Went to the store to buy 2 items only to find out that there is a mark up price on 1item the lady at the till said she is sorry for the price change but theres nothing they can do then i ask who's fault is it because i saw this price but when i have to pay they tells me different price she said it's there's but she can't assist then i left that item instead and buys only one,so in future can they please make the right prices to avoid such incidents it really frastrate we customers because it's time consuming