Sandisk - Sold Fake Product to customer without Bill

Hello Everyone ,
I purchased a Sandisk **GB Sd Card from a Local store "National Watch house" in osmanabad , Maharashtra . the MRP of the product is **** , Bargained and sold to me at *** . But right after i went home the card got currupted . I Contacted to the Sandisk customer care they said the card your purchased is fake . I went back to the shop and told them you sold Fake Rebranded product which is also known as "First Copy" or Replica . I asked him to refund back my money , he denied , blaimed me that i would have inserted some sort of virus in it . Instead he is accepting that its a fake product but he is saying once sold is sold , still after so much rrquest he is ready to replace but he is replacing it by same new fake package of Sd card . What should i do ? I want my money back . Ill purchase it from online platforms .