How to stop builder from giving parking lot which was allotted to us

we purchased a flat in 2006 and shifted there. it was not completed and the original layout which was passed was parking in basement, ground +5. builder changed the plan to 6 floors & a small flat in ground floor. the builder had planned ground floor and wrote vaguely the parking locations in transfer deed for most of 12 parking except 3. now as plan is passed and 6th floor is sold builder wants to construct flat in ground floor and he wants to shift us from our parking to smaller on . on the our deed just one parking is mentioned and we are occupying one as he verbally told me. what steps we can take that that builder cant shift us from the parking we are using for 13 years based on his verbal confirmation. in all the 12 flats he has sold in the apartment, the specific parking we are occupying is not mentioned in anybody's deed. can he give any letter to anyone else for the parking we are using. is there any way to stop him from doing so.