Is providing parking I open area in a society legal ?

We are staying in an apartment of around 500 flats. All the flats have a stilt parking marked and allocated except 3 flats for which the builder agreed to allocate in open space with a shed. Now after constructing the 3 sheds, he is marking all open spaces with car parking and selling to flat owners who have second car. He is charging money for this but providing any legal receipt. This practice has severely reduced the open space and made the entire place congested, including the common approach roads where he has marked on one side. After a meeting with the builder he claims that it is a normal practice to do it and he has few 1BHK houses(45) which do not have stilt parking. He says it is the right of those people to get a parking inside the campus and so he will allocate to them on first come first serve basis, and also to people who opt for second parking by paying the cost of the parking. Can I know if we can legally challenge the builder and get all the open parking dissolved