Need advice about the plot cancellation by developer

I booked a plot in a shamsi town at super highway. However, i have not made a 100% installments. Around 85% are paid while 15% are remaining. My developer sent me a legal notice for clearing the dues within seven days otherwise it will be cancelled. We reached on day 8, he refused to accept the payment and saying that you will receive the payments in seven days of your booking. Kindly advice for the legality. Is the first legal notice will be enough? How can i take the legal action against their illegal step?