Irregular charging of service tax by builder

Dear Sir,

I have purchase a residential floor in Mohali from Tanjeja Developers and Infrastructure Limited. The cost of floor is Rs.3162500/- and it was booked in December 2009 with an advance payment of Rs. 436250/-. Before 1-07-2010, the builder had completed approximately more than 85% construction and had raised the demand of Rs. 2420000/- (as per statement provided by builder) to me. But I had made this payment in December 2010 with interest. 

In September 2011, I have paid the balance amount to the builder with service tax (service tax on balance amount) and taken the possession of my floor. But while doing process for my registration of my residential floor in Dec 2011, the builder has not provided me NOC. He claimed that I have to pay service tax on payment made by me in December 2010 also. Is this correct?   

I under stand that tax is related to services provided by builder (construction cost of floor) after 1-07-2010, not related to payment made by the customer after 1-07-2010. I had also put the mail on 11 Dec 2011 to builder to get clarification on this. But even after two or three reminder, till now I have not received any reply from them. A copy of mail sent to the builder is attached here for your reference.

Please help me to understand the things and if I am correct, please tell me how to proceed with the builder further.

Thanks and Regards

S.N. Mittal