Car Parking Allotment not given by builder in Mumbai Housing Society

My building went under redevelopment and a new building was constructed of 7 Floors and 15 flat owners of which 5 were old owners. These 5 old owners were promised 1 parking each as per the agreement. However, after the building was redeveloped, the builder has refused to give parking allotment letters to these 5 old owners. However, he has given parking allotment letters to all the new owners. The building has 22 stilt parking and 5 open parking. Builder had promised this 5 open parking spaces to the old owners. The building plan says 2 parking each for flats with area greater than 70 square metres. All the 5 owners have a home of 72 square metres. What are the next steps that I should take?