Builder not providing parking

I took possession of my unit in2015 wherein BBA mentioned one parking shall be allocated on first cum first serve basis. After some follow-ups I got a slot allocated . However since I did not occupy or rent out the flat immediately, some time later an RWA was formed who reallocated the parkings according to their whims..in effect my parking slot was allocated to someone else. Apparently, there are lesser parking slots Vs the units. Ever since I had been chasing the builder but to no avail. Though as per his original site plan my unit no is showing in the parking slots available because I was one of the original occupants when occupancy was not more than 50-60%. Now despite charging maintenance the builder has not ensured the safety of basic amenities like parking which according to me has been trespassed by the so called RWA who according to me should not have any right to reallocate a parking which is already allocated to a buyer esp when I have been paying maintenance to builder not RWA