Allotment of Car Parking Slots by Builder

I have purchased flat in multistory apartment complex along with 2 covered car parking spaces in the basement. Both Car parks are included in the sales deed under Schedule "C" (Description of the Apartment) with out identifying where in the basement. We have two basements, upper and lower. Builder charged same amount of money for each car park from all buyers. For us this was done in 2010. Last one year people started moving in and now Builder started distributing the car parking spaces. There is no basis of the distribution, like as per the booking done, or first come first or based in possession or based on moving in the apartment. A general rule is being said that below 15th floor all will get lower basement and above that upper basement.But that is also not being adhered to and it is based on builder discretion. I have raised voice that there should be based on some principle but builder is not listening and has gone ahead and allocated the parking spaces. What should we do, as the parking given to me is not acceptable to me, this is simply arm twisting.