Bad customer service and fail adverti*****t

It is with shock the level of bad customer service me and wife received. Supa store is now doing fails adverti*****t on their products they selling. They had a promotion of Delush Natural Sweet Red Wine "3 for R100". To our shock, when we got to the till to pay. The cashier told us the special/promotion is for 2 wines for the price for R75. I then said I want to see the store supervisor or store manager. A short to medium height lady came through and I then told her that the promotion says 3 for R100 on the Delush Wines. She then answered me with an attitude, saying there's nothing she can do as the buyers aren't working today. She then walked away with no care in the world. I am not angry because my wife ended up saying we should take the 2 for R75. Maybe Supa store should display such promotions if it is not true...