Builder not refunding the booking amount even after deduction

Hello, I am Bhupinder Mittal. I along with one of my friend bought studio apartment from Imperia in Sec 37, Gurgaon in March 2012. We have paid around 9 L of the initial payment and was told that we will get the possession in 3 yrs. We didnt receive any demand until Dec 2015 and then we suspected the project is not approved which is causing the delay. then we decided to surrender this unit - on asking the process they said they will deduct 15% of the paid amount and the balance will be credited to us in 3 months. We agreed to that and completed the said formalities on legal papers and send to them in Jan 2016. When we contacted them in April,2016 ( after the three months are over) - initially they said they are still reviewing our request and after follow ups for one month they said - management has decided not to refund any amount and all the surrender applications are put on hold. We are clue less now. We are corporate people and don't even aware of the legal proceedings or how to approach consumer court. Can you please help on what action can we take against Imperia. Many thanks Bhupinder Mittal