Higher price than MRP and frequent hassle based on it

Location/place: Flat 9, Sumit Building, Rajasthan Hsg Soc, JB Nagar, Andheri (E), Mumbai

Name of company/service: Gupta (Mom and Pop store)

I have been purchasing goods from this shop since a couple of months now. The owner (Mr. Gupta and his son) charge goods above their MRP. I generally purchase Mother Dairy Milk – MRP INR 14.50 for half litre. He charges anywhere between INR 30-32 for 1 litre.
When asked the reason why he replies “its the rate of the area/service charge/cooling charges” etc. I am really fed up with this store today since it sold me soured milk and on top of it didnt take it back. Also the story doesnt end here there was a big quarrel between both of us with the high MRP and rude language used by the store keeper for not giving INR 32 every time but INR 30 on most of the times.
Kindly have a look into the issue and curb such kind of malpractices in the market. The question is not about a rupee or 2 but it becomes an issue wince this additional buck is not registered anywhere and is black on which Govt losses out IT.