Complaint

I was at Spar Express at 331 Rivonia Blvd in Rivonia on the 3rd November where I was making a purchase of Snaks. The cashier was Anikie. The snaks were on promotion when you buy 2 for R22. When she rang the snaks I saw that they were not going for R22. I told her 3 times that those snaks are on promotion instead she said to me "it's only a difference of R2".. How does Spar Express runs a promotion that consumers can't be granted? She clearly refused to give me and she had a nerve of telling me "it's only a R2 difference" really