Cancellation of booking of flat

Hi all,

I had booked a flat and paid 2.5 lakhs towards the booking of the flat. But due to certain reasons I had to cancel the booking of the flat. The document while booking of the flat mentioned that Rs.50,000 would be deducted as the cancellation charges. 

My problem is that now the builder is saying that he cannot give me refund unless the flat is booked by some other party. This point was not mentioned in the documents when I was booking the flat. 

But now the builders are refusing to refund my 2 lakhs stating that it is thier company policy to refund only when the flat has been booked by some other party.

Please guide me as I need the refund for some medical purpose.

Thanks in advance.

Naushi