Product with less weight in packet

Location/place: Ranchi

Name of company/service: Bisk Farm

I had purchased 2000 packs of Rusk for party.Buy chance the last packet that remained , I happened to weigh.As against 180 grams mentioned in pack I found that to be 168 gms.so I have been cheated in all 2000 packs.
And moreover this may be happening to product across country.
The details of pack is Suji Rusk of Bisk Farm.LOT No.OT2J1D.
My contact no. 9431103203.
What is the action that you will be taking against the company and what compensation should they pay me.