Should i pay extra tax while purchasing goods on bills in Inida?

After implementation of  VAT in india retailers are making extra money for selling goods on bills.
Suppose i bought a branded ceiling fan in Delhi and retailer have quoted a price Rs.1200 nothing else but as soon i asked for a bill he told me to pay  12.5% VAT extra on Rs.1200.
In VAT system retailer purchase goods after paying tax to the manufacturer it means whatever tax he has paid to the manufacturer is already included in his cost and that should not affect by taking bill or not.
Only VAT on retailer’s markup is to be added if i take bill from him not full tax on whole amount. In this way retailer are making fool to the consumers. Further what they do, they sell the bills to a seprate person and earn extra money by selling bills without goods.
By this excercise they are evading income tax as well as VAT and cosumers are suffering. So please always negotiate for including VAT pricae and ask for bill.