I found someone's else debit card lying on the ATM machine today.

So, I found a debit card lying on the top of ATM machine today unattended. I waited for five minutes in the hope that the respective cardholder (Harish Kukreja if you're on reddit) would arrive and the guard was neither there. I took it with myself, called the customer care and got the card blocked. The representative confirmed it's done and a text is send to the account holder. Harish if you're worried, do not anymore :)