Bad Experience - Meat Good Ga-Rankuwa Industrial

What a discussing service at Meat Good Ga-Rankuwa Industrial. So we went to buy a box of Weetbix 900g, on the shelf their price tag said R46.99 however at the till it was R66.00. A whole R19.00 difference to be told that "they are forgot to remove the" old" price. The cashier was rude as well as their manager. When I told them of CPI, I was told that that index doesn't apply to them. Please can someone advise regarding this.