The first step is to call the customer care of your issuing bank and block the card. Then, you can dispute the unauthorized transactions that have been made on your card. Usually, the disputed amount is blocked on the card until it is resolved and the customer is not liable to make any payments until such time. With most banks, customers have zero lost card liability provided that they report the lost or stolen card within the time stipulated by the issuing bank. You can also get insurance coverage for such transactions.