1. The builder can never forfeit any whole amount .
2.if there is a penal clause he can deduct a reasonable amount for the los suffered by him out of this cancellation.
3. So send him a legal notice asking for return of your whole amount.
4. IF HE DOES NOT RETURN THEN FILE A CASE IN THE CONSUMER FORUM WHEREIN YOU WILL GET FULL REFUND ALONG WITH DAMAGES AND COMPENSATION.