Fraud by property agent

Respected senior members I entered into an agreement to buy a flat in a dwarka society. The property agent told me that the seller has signed agreement with the owner and the owner will execute sale deed in my favor. He also asked me to pay 5 lacs ruppes through cheque to owner which I paid.Rest of earnest money of 10.5 lacs paid to the other man who have signed agreement with me.The owner has also witnessed agreement and all receipts.Last date of balance payment was 15 th Jan.Later it turned out that flat sold to me have been extended to 3 bed after freehold conversion .No approval shown to us so we decided to cancel the deal The delear also agreed to pay back the money received .However now he is avoiding on one pretext or other nor he got the date of agreement extended. Although I have sent a letter stating all this ti sub registrar before 15 th Jan.I trusted the dealer and got cheated. Plz suggest the way by which the delear can be forced to pay back. Regards