Cancellation of booked flat

I had booked a flat (initial cost = 10% of total cost) in month of April 2015 in pre launch offer . I signed a application form which had terms a conditions for cancellation that 25% of agreement value will be recovered. project was not fully approved at the time of booking. I signed sales and construction agreement in Aug 2015 which had condition that in case of more than 120 days of delay in payment demand , a notice will be sent and if buyer does not pay within 15 days from date of notice then earnest money will be forfeited. In month of Oct 2015 I had a mail for first demand which I had to pay within 1 month. but in month of nov 2015 I was admitted to hospital for serious medical conditions and treatment was suppose to be for 4 months So I sent him a mail for cancellation of booking and return full refund on basis of humanitarian ground. But sales person verbally assured me not to cancel booking and get the treatment done. He would fully waive off interest accrued. Now he’s ready to waive off only 50% interest or deduct 25% of total amount paid so far. After expensive and exhaustive treatment I am not wiling to go for the project so I prefer cancellation. So are there legal options to recover amount deducted by builder?