Booking amount refund

I have booked a 2-bhk flat in Hyderabad. However, as a booking amount the builder collected 2.5lakhs from me and before booking he need my details for application purpose and never mentioned me that it is an agreement. And more over he didn't handed me a copy of the agreement which he said as an application while collecting my signatures. My family verified that the carpet area is very less as the word given by them and initially the sales person showed that there will be two car parkings provided and then he changed the stance after booking happened. Due to all these developments i lost the trust in them and informed them i will cancel the flat booking. Then they mentioned me that terms and conditions exists and i signed at it. Now as per the terms and condition they say only 50% refund will be there and that too i will get after the flat re-sale happened. I didn't took much time in informed my cancellation decision to them i.e. within a week of booking i informed them. I feel cheated and totally lost faith in them. How can i proceed further legally for getting my re-fund back.