Punjab National Bank [PNB] — unauthorised transaction

There was a transaction of rs.36000 from my bank account which i did not make. I received an otp of rs.36k txn on amazon and i didn't share the otp with anyone. The amount got debited from my bank account and i reported immediately to the pnb bank but still i've not received any update or refund from the bank. I request pnb to look into the matter and refund the amount.