1. Open /Stilt /Podium /Basement Parking spaces are all classified as "common open spaces" & Free of FSI, under the Regional Town Planning Act and CANNOT be "legally" Sold or Purchased or Registered or Leased. Parking spaces can be allotted (most of the times by illegally collecting money, which is a criminal offence).
2. You can file a Police FIR, requesting investigation and charge-sheet, for offences like Cheating, Intimidation, Fraud, Breach of Trust, Mischief etc.... against the builder person, supported with all relevant supporting Documents, Evidences & Witnesses.
3. IF the Police does not take action, THEN you can file private criminal case u/s 156(3) Cr.P.C., in the local Magistrates court, seeking directions to the Police to investigate and file charge sheet. The said Person may come down for settlement.