1)issue legal notice to association that parking lot allotted to you is not functional as it is not possible to park your car in said slot
2) that no proper procedure was followed for allotment of car parking slots
3) builder has no powers to sell the car parking slots . once association is formed it can allot car parking slots by drawing of lots if number of members are more than slots available
4) you can move court against association if association dos not redress your grievance