Parking dispute

I got my flat registered in 2013 . In the registry , i have been allotted 2 parking slots. One of the slots i was not using . instead i was parking at a temporary slot near the lift lobby ( for convenience) with the consent of the facility maintenance company ( no written document though). Now, this temp. slot has been withdrawn citing blocking of driveway by the new RWA. The facility management company has also got changed. Now , when i decided to park at my original slot ( as per registry) i found that the builder had allotted ( sold) this slot to another resident too. The registry of this other resident has happened AFTER my registry. The RWA has declared this slot disputed even though i have argued that by virtue of getting it registered first , i am the legal owner. The builder is not responding properly. The other resident is also not at fault as such. I wish to claim my parking slot . What steps can i take? Legally what is my position . Need a legal opinion