Bank renting fraud case broker not returning money

A broker introduced himself that he will rent a bank to our premises. he took advance from my father saying that stamp papers and other necessitates need to be generated and he took 5 lacs from my father. My father gave him bank cheques. Later, we got to know that person is fraud.It has been around a year we are asking our money back. He says he will return but he is not returning a penny. When we ask forcefully he says, go whatever we want to do , we can do. We have the phone recordings and he has signed on one stamp paper that he will return the money. But still we are not able to get money. That money which my father gave that broker was for my sister marriage. But brokers consent that bank will give advance deposit it will be further used foir her marriage. But still the broker is fraud. Relatives told us to do FIR but that does not sure that money will come back. please help