False Advertising at BP Rockys (Grassy Park)

went in to the BP Rockys shop this morning to buy some stuff for work today, as you walk in to the shop they advertising Monster and Doritos Chips for a special of R19.00 incl vat for both items, so i decided to take two of the specials, and some other stuff ,as i got to work i checked the slip and i was charged R25.20 including vat, now this is unacceptable and its against the law, i will be taking this matter further with The Advertising Standards Authority of South Africa, and i will be posting on social media on How BP are advertising false.