Unfair business practice

Good day I went to Edgars Gateway today (17/05/2025).I saw Stone habour Jeans with a promo code "take 2 deal".I took 2 pairs of jeans bit when I arrived at the till point I was told that the promo is over but stickers of the promotion are still there.i paid the gull price but I feel it's unfair when the promo is over remove the stickers on the items.