IDBI Bank — debit card hacked and financial loss

Address:	Mumbai City, Maharashtra, 400032
Website:	inet.idbibank.co.in

Sir,
Yesterday, on 23rd july, 2017 at 10.07 am i have received sms from idbi bank that rs. 343.44 was debited towards debit card transaction visa-poi/moun. Us. (Mount calvary lutheran ch excelsior us)
Immediately i have called on [protected] and asked about the incident, i got a reply that if you have not used your debit card, then it must be hacked, so accordingly i have requested them to block my card immediate, to avoid further transactions.
I am yet not understood, that how can some one from us operate and made transaction on my debit card.. Since, the card is in my custody, and i havent used it on any internet portal.
Is idbi banks card security is so week, that anyone from other countries hack it"?
Please enquire about this transaction and do the needful to find that hacked and credit my amount rs. 343.44 in my account.. Also advice me for any further assistance required from my side.