1. IF there is no registered society as on date of your purchase agreement, THEN such demands amounts to extortion & intimidation, more so since such transfer fee amounts CANNOT be reflected in such any unregistered body /society /association /whatever ....
2. You can file a Police FIR, requesting investigation and charge-sheet, for offences like cheating, intimidation, fraud, breach of trust etc.... against the person, supported with all relevant supporting documents.
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.
Keep Smiling .... Hemant Agarwal