Wrong price

I just went there to buy the Amandla super maiz meal 25KG, on the shelves it was on special for R204.00 but whe I got to a till to pay they charged me R215.00. When I ask about it the cashier called another lady she said is a supervisor, I explained to her, then she went and check and took more than 10min and came back and said no it was not Amandla that was on promotion bt it's Kings. I explain to what I saw there and the lady that was helping me agreed that I'm not the first customer to query about this. Very disappointed cause they make it as a huge drama as if I don't have money to purchase. And that lady's attitude was very bad. What makes me more angry she said I must show her the proof of that promotion while she went and remove it.