1. As per records, you have already paid him the entire amount before the sale deed was registered in your name. The builder can not cancel the said sale deed.
2. Never accept/mention the fact anywhere in your letter/email/discussion that you have not paid the entire consideration. You need not ring him. File the consumer case as suggested in my earlier post if you have not yet received possession of your flat. It will be a very good case to win.
3. the flat already stands in your name. So, you can claim its possession. If you wish, you can pay him any amount showing it as extra amount paid but never write anywhere that you have not yet paid the entire consideration.
4. The builder can refuse to handover the possession of the said flat for which you shall have to approach the Consumer Forum as suggested in my earlier letter.
5. If you pay him the said amount, mention it as an extra amount as demanded by him and never mention that it was due from you. My suggestion will be to pay him the said amount only after taking possession of the flat.
6. It will be prudent on your part to pay him the amount only after receiving posession of the flat. iuf he does not handover the possession, approach teh local District Consumer Dispute Redressal Forum as suggested in my earlier post. You can execute a POa in favour of anybody in India by getting the print out of the said POA on Rs.50 stamp paper from your Indian Advocate and then sign it before the appropriate officer of your local Indian Consulate for returning it to your POA holder in India to file the complaint case for and on your behalf.
7. Engage a local lawyer having expertise in this field.