HDFC Bank — unauthorised transaction

Address:

Kolkata, West Bengal

Bank: HDFC
Branch: Jodhpur park
My details: Goutam Nath
2, Maharaja Tagore Road
Kolkata 700031

Hello experts,

I am a customer of HDFC Bank Holding an senior citizen saving Account. I am using my card for my daily transaction through ATM or Online banking. On 20th January 2019 while checking my bank statement online I have noticed that somehow my 2000.00 + 2000.00 = 4000.00 has been deducted from my account thru unknown pay zapp account. Statement shows that Money has been withdrawn thru net banking (Screen shot attached) even when card is with me all the time. and I was Home on same day. That means somebody access my account

I need your advise how to track this issue, can it be bank fault or its a 3 party fraud or its a mistake by bank. I have already logged complaint to HDFC bank. How may i claim my money but HDFC Bank ignored their fault.

Regards
Goutam Nath