The frst thing you have to day is deny the transaction and refuse to make payment as it is fraudulent, due to duplication of such card and warn them turning the account as default and any adverse comment on credit rating may compel you to claim extra ordinary compensation for loss of your reputation and damage to prestige.
Then, File RTI Application and seek entire information through certified copies right from lodgment of your complaint/protest and till findings in their investigation report. In RTI Application seek information through a separate application as to the complaint has been filed as the complaint has been made by constituent, and SB is an affected party/victim.
After getting information from Bank, you will be knowing exact location, date and time where the fraud has been perpetrated.and build up the alibi that it is impossible for you to be at Delhi and Bangalore at the same date and time (Example)
Let the Bank commence proceeding and then contact advocate for further guidance in defence.
Wait for one year from date of lodging protest (first step as above) and within 2 years file consumer complaint as party in person, equipped with facts and the costs may not be more than Rs.500/- to file complaint and argue in person.