Monarch Universal Group — monarch greenscapes, panvel

I booked a 1 bhk flat in monarch greenscape, panvel navi mumbai (Launch) and paid whole amount to builder and also got registered paper from panvel registrar office. That time builder told possession will be in dec 2018, this was also mentioned on site. After sometime, we got transfer to jaipur rajasthan and been disconnected with project status. Some time back we got through newspaper that builder has cheated many people and there are so many cheating cases registered on his name. We travelled mumbai to see the status and also tried to file a complaint in belapur police station, but nothing happened. We have all legal papers but don't know what action can be taken? Please help us.