Upmarking prices for discount

We heared about the 30% sale at Trappers Northridge Mall in Bloemfontein and went there on Sunday 21 July 2019. We purchased a pair of Solomon tekkies for my husband. Marked price was R1999 and we got 30 % discount on that price. My husband decided that I should also get a pair and we went back there on Friday 26 July. (Only 5 days later) When we payed we noticed that they were more expensive and queried the price. We were informed that the stock price was incorrectly marked and they had to reprice the items. That means a 10 % increase. Why is it that when your store has a 30% discount on the marked price the marked price is suddenly esculated by 10 %. The discount then only 20%. That is misleading adverti*****t to the public