incorrect Pricing on boys tshirts

i did my shopping at Mr Price Diepsloot on the 17/05/2019. There was a flash poster that said two for the price of two, i asked one of the Store assistance and she confirmed that its two kiddies tshirt for R80, When i got to the till to paid the pricing was correct, i told the cashier to go check the board she confirmed that i'm correct. she called a Store Associate Zintle Sisanda Lingani who blatantly refused to do a price override even after i explained. i nearly walked out with out paying for the rest of my clothing, I left the tshirts that were wrongly price. i honestly love shopping there but i cant always argue with the staff when it comes ti pricing.