well welldo you mean the otp has been exercised? if so sure you can sue them.
if you just paid the 1k and the seller did not want to exercise it, that will be tough.
your agent can ask his company for legal action.
excercise opt is by buyer, not seller.....
buyer just needs to sign at page 8 and pay the stated excercise fee, then both parties are legally bonded.
Huasing Association 1999 - 2013