Earth infra is Fraud

Location/place: Pune

Name of company/service: Software engineer

I have booked a flat in one of the projects of Earth infra at Noida extension. Under their flexi plans I have almost paid 70 percent of the flat amount and still work is not started. I doubt i will ever get the possesion. Please guide me what to do from here. I asked for the change in the plan but they are saying money will not be returned. Please suggest what should I do.