Indian Overseas Bank — online fraud from my sb account and request for refund

Address:

609001

I am a customer of iob of mayiladthurai junction branch. Some one has misused my account and transferred amt to the extent of 15000 online in a single day. I have no sms, no atert for the said transactions. When i happen to see the account to my surprise amount was transferred to filpkart three time totaling to 15000. Immediatetly i block my account and registered a complaint to bank in writing.
The authorities are unable to give a solution to my problem instead asking for questions as if i have disclosed my details. They also directs me to go to police instead seaking a solution from bank.
I speak advice as to what should i do so as to get my money back.
Regard
Customer