Actions that can be taken against shops charging more than MRP??

I went to buy an ice cream today. The shopkeeper charged literally 5Rs extra for that stating some bs reasons like fridge and all that..he was like if u want you take or else leave. Since I wanted ice cream, I gave him extra 5Rs and left.. When I said case can be filed against you, he replied idhar yesa hi hota hai karlo jo karna hai

This has happened earlier many times..is there something that can be done with these without actually getting into legal stuffs like case filing etc? As I am still a teenager I don't actually want to get into legal stuffs, yet want them to stop overpricing... i