Not refunding booking amount. Booking cancelled. How to recover money?

Reminders to your new address is enough evidence to prove that the builder company records hold your new address. Without giving you a proper notice, i.e. a notice that reached you at your new address which was also in their records, in case they cancelled your booking and also the booking amount, it amounts to an unfair treatment meted out to you.

You need to look into the initial agreement signed between you and the builder company, and if it does not give any power to the builder to cancel your booking and unsurp the booking amount without giving a proper notice to you, you can file a suit for recovery of booking amount, if you want to recover the amount paid to them so far.

If you desire to maintain the booking, and the contractual provisions provide such a scope, you can file a suit for declaration in the relevant Civil Court.