Car Parking in residential area.

I have purchased a 2bhk in Kalyan and got the same registered it about an year back. At that time the builder had told me that he will give me an allotment letter for stilt car parking (verbally), he gave the same to me. Car parking is nowhere mentioned in the agreement. Only document I have is the allotment letter for stilt car parking given to me by the builder. Now the society is formed and few members (who don?t have the car parking allotment letter) are objecting and creating disputes regarding this car parking. My question? 1)Since builder has issued a stilt car parking allotment letter can any body including the society oppose the same and prevent me from parking my car? 2)Is this stilt car parking allotment letter valid legally? Please advice?