Runwal Group — Booking amount not refunded cheated us on payment terms while booking

We had booked flat in dombvli runwal gardens. We had been told that will have to pay only 2.5 now and remaining after 6 months and the stamp duty would be bear by builder. Suddenly one day before expiry of a month from the date of booking we got CRM called stating that will have to pay remaining 2.5% in 1 day otherwise flat would be cancelled. Who can arrange 2 lakhs in a day? Why we were assigned crm one day before expiry these all are their plan.