Unfair pricing due to the fact that I'm a person of colour and purely undermining customer rights

Scene Engine garage Montana,next to Montana Junction-it is a consumers right to be treated fairly and equally as a resident of a country or not I was fairly untreated and given a very terrible service ever only because the people in that garage undermine and take for granted of people like me not knowing the capabilities of customer power. I went and bought a monster energy drink only to find that on the shelve it costed R12.90 but at a teller it costed R19 I asked for it so they refused to overide the transaction I asked for manager when the manager( Ntombi) came she firstly gave me attitude and started by saying you won't have it before I even explained said anything after a while of disputing the price and explaining my rights she just said I won't be able to help you I went and explained to the second manager named (Denie)he told them to hand it but later changed his mind and walked away i went back to him he refused little as it may seem I wanted to know to ist how service and how our rights as consumers in conviniant spaces are being abused by managers or stores that simply feel they do as they please which is very unfair imagine such an inconvenience in a an expensive item who would pay the difference I'll continue to push it as my right