IndiaBulls — Refund of booking amount

Address:

Mumbai City, Maharashtra, 400010

I had booked a 2bhk flat at indiabulls greens panvel phase ii in may 2013. i paid 20% of the flat cost for the booking. the project was to commence in 6 months but did not.in november 2014 ib informed that they would refund the booking amount with 12% interest or i could stay invested. i decided to stay invested.in december 2015 ib informed that all approvals have being received and work would start shortly. they informed new flat number and additional cost of @ 5 lakh. i decided to cancel my booking and asked for a refund. ib informed me to submit various documents for the same. after submitting the documents in february 2016 they informed me by email in may 2016 that they will deduct 10% of the flat cost plus service charges. after various emails they have informed that they will deduct 5%.
Please advise how to proceed.