I thought it's scam and decided not to respond with Y or N, But then I receive phone call from HSBC. It turned out it's not scam. If you receive such text, It's better that you call HSBC, Than just ignoring it.
It is not a scam. I received an SMS from this number saying that there was a possible unauthorised transaction on my card (someone tried to withdraw 10 000 Indian Rupees). After phoning HSBC, I found that the SMS was genuine and there was indeed a fraud attempt on my card.