Sold for consumers more than MRP

Location/place: Kotturpuram Chennai

Name of company/service: Mazza – the cool drink

Hi,
I went in to a restaurant in the kotturpuram signal and asked fora mazza. I paid Rs. 20 as the label in the disposer was point to Rs. 20. The man said it is Rs. 30, I looked at the MRP it is mentioned as Rs 27, I asked him why is he charging 3 Rs more. He said this was charged by the company at Rs. 30 and he has an invoice. He said if I am not interested I shall level it back. I checked wiht another petty shop in the same locality, there also I was told it is Rs. 30. I don’t know why it is being sold more than the MRP. People are fleezing money at this summer time with all the cool drinks and water bottles etc.