Parking Issue

Dear Sir, There are 9 flats in a builder apartment including once flat constructed on ground floor and half area is open for common parking. The problem is 8 owner got car and there are space to park only 4 car maximum. While purchasing the flat builder said you have one car parking space at ground floor stilt parking and he has mentioned this in everyone's flats registry document. Now the issue is parking space is for 4 car max but he have allotted the space to 8 owners. While chasing the builder he told that we have mentioned in document that this is common Area for car parking you first come first get basis. He is not giving any solution. I have read other issues on this forum and understand that stilt area should be kept open but here builder have buildup a flat in 750 sqft area which suppose to keep open. we all are the middle class family and have purchased flat from home loan and have invested whole life's savings in it. please help us and suggest what we can do to come out from this problem. is there any legal way? thanks a lot.