Consumer Redressal

i have booked a flat at kohinoor maxciti,which is in chikloli village,ambernath, thane developed by kohinoor infra developers.at the time of booking i gave rs.5,00,000 .his salesman harassed us for five to six months saying registration will be next week and delaying it day by day and after six months he cancelled the flat and refused to provide the reason for cancellation.and when i asked him for refund he told us to write a cancellation letter saying that i am cancelling the booking of the flat due to financial problem and without cancellation latter he will not give us the money.and later i gave a cancellation letter saying due to financial problem i am cancelling the flat and builder also gave us a cancellation form and took signature on it.they both took rs.5,00,000 at the time of booking and kept it for seven months.builder returned the money without paying any interest & expenses.