i had booked a residential flat in a multistorey tower in 2009, for approx 60 lacs to be paid in instalments.builder gave a allotment letter which incl the cost of the flat, the carpet area of the flat and the payment schedule. builder further gave a letter that possession would be given by jun 2013, failing which he will give 9% interest .he has not finished the project even now i hav paid 81% of the flat cost. Now he is demanding more money which is not as per the payment schedule, he was to complete the RCC work including all slabs first, due to not getting cc for upper floors he started brick work and plaster without completing the upper floors.i told him to complete the upper floor RCC WORK first, and take payment as per payment schedule.On his insistence i agreed to pay this amount also but insisted that he commit the new date by which he will complete the building and hand over possession of the flat.Builder refused to commit the date of possession but threatened to cancel the flat allotment if i did not make the payment. THE FLAT HAS NOT BEEN REGISTERED .Can the builder after 5 yrs waiting and 81 % payment cancel the allotment on the ground of nonpayment of dues?what should i do ?