HDFC Bank — fraud/unauthorized transaction

Address: avadi, chennai

In my account unauthorized transaction has happened on 3 aug 2020, the transaction type is (Vctf #cardnumber#) of 14991 rs. I made a same amount transaction on 3 days back. It got deposited and the transaction got over. Without my knowledge the same amount has been debited in my card, no otp, amount where it gone i do no. So try to help me with this type of transaction.

Bank saying that the transaction has been made by me. I cant get the solution for this.