Allotment of Car parking space by builder without consent of society members

Dear sir, We have booked flat in high raised society in 2015. At the time of booking & finalizing the deal builder had informed that every one shall be having one allotted car parking and same is written in our brochure. As we were first few to book flat, we asked to confirm where our car parking slot shall be. We informed that we would like to have best covered parking at ground floor in slit area in front of main entrance of our flat. Builder had informed that as you are first few they will provide best parking based on first come first basis. We also asked to provide & show us the parking plan & layout but he did not show that. Then after from mid 2016 onwards, as we come to know, builder has started collecting parking charges Rs. 50000/- per car for premium parking on ground floor stilt area and Rs. 30000/- per car for basement parking at basement area. It is also come to our notice that builder has not given any seperate parking payment receipt to any flat owner. Now, recently builder has started issuing allotment letters & their parking based on payment received. He has not given us any allotment letter even though we were the first few to book flats in 2015 & had assured to allot best parking slot based on first come first basis. However, he has marked our flat no. on society wall. Do to such partiality in allotting the parking slots, members are also quarrelling with each other saying why I have not been given this slot? and those who (nears & dears) got good slots, shouts please do not park vehicle in my place etc. etc. Sir, what should I do as builder has not given me covered parking in stilt area as informed based on first come first basis.