Parking allocation by builder

Hi, This is regarding the car parking allocation. I have recently purchased a flat in Pune and while purchasing the flat builder ensured me that he will allocate the parking on first come first serve basis (the same is mentioned in agreement). Recently builder has allocated parking to all the flat owners on first and first basis except 4 parkings, I got open parking. There are 4 covered parkings under the building which are not allocated to anyone. I have asked builder why they have not allocated these 4 parkings to current flat members as you have told us that you will allocate the parking on first come first serve basis? Builder replied to me that if you want any parking from these 4 parkings you have to pay us 3 Lakhs ruppes extra. I was shocked to hear this as the parking comes under common area and we all flat owners have paid for this and builder cannot sell this area. This is illegal practice by builder and trying to make some extra quick bucks through these 4 slightly bigger area car parking. I have sent many email to builder to allocate the parking on first come first serve basis but didn’t get satisfactory response from them. Now I don’t have any option except to take legal action on builder. I want legal advice from you on this. Please help me on this.