You are not addressing Apple here - they don't read these posts. This is strictly a user-to-user forum and everyone responding is another user, not Apple. No one here cares one iota what you say or do.
This is an AT&T phone and you have no right whatsoever with them to unlock it since you never were a customer. Apple does not unlock phones for anyone.
Your problem is caused by the store that sold you what is probably a stolen phone, one that never can be used in India.
What's really astounding is that you waited 2 years with a useless phone and did nothing until now. Very, very hard to beiive anyone would do that.