VAT is charged on MRP OF soap, oil, etc

I buyed product from bigbazar and they had taken vat in the bill which is charged on all products, my question is, it is legal to charge VAT on products like soap, oil which have MRP on it, if that is right the the same product I bought from other retailer its also a shop like big bazaar but they did not charge VAT.
If big bazaar is doing wrong then the money collected by them will have to be refunded and they have to find for doing it.