Fraud dealing by broker

Brokers finalise flat with us in mohan tulsi vihar phase 3/ 4I /204. We on checking papers handed over token amount of 1 lakh via cheque on 16 november and started bank loan process from HDFC bank. On having loan sanctioning letter we on 27 Nov gave another cheque if 9,25,000 to that party in Singh office via cheque. They told us to transfer stamp duty amount to stamp vendor ravindra jadhav on 29 Nov which was through NEFT and promised the registry on 1 DEC 2018 but when process was getting delayed and NOC was not issued by society on 30 Nov, we came to know same day along with chairman of society that flat was already sale to another tukaram takle in Feb 2017. Chairman was also unaware if this dealing. We asked broker, they said they will manage but this was directly fraud and we were shocked that how come brokers do such things. Still they were saying you had given by cheque don't worry but when we had paid 13 lakh along with stamp duty then why don't we worry. We are demanding our amount return then also they are not returning ,today tomorrow, things are moving like this. What should I do.