Charging over and above mrp on railway platforms

At agra cantt railway station at a food stall n.O.14 vendor charged me rs.15 for a water Bottle and rs.15 for a biscuit pack and on asking that its mrp is rs.12 for both he said very rudlly that if you want to buy then you have to pay rs 15 then I said I LL complain on sayng this I found that he was not having any fear of complain. I would request the concerned authority to look into the matter very seriously.