Tata Housing Development — Compensation against cancellation of residential property Tata Aveza

I booked my flat in Feb 2014 in Tata Aveza Mulund project as original booking. I had paid so far over 2crores. Now they got into troubles getting some clearance and cancelled the booking and returning the money with 9.3% simple interest only on principal amount (excluding taxes). They had charged 18% interests for the delayed payment.
I expect them to pay 18% interest on the entire money that I had paid to them. I had huge mental pressure abs agonies over last 8years.
Please help me settling this matter.