A person serving in central govt.cheated my father by getting money promising to transfer the leased house after certain period and not doing it. Afetr having money for 3 years that person gave back the money and asking us to vacate the house. He had given a written statement in Rs20 bond paper that he is agreeing to transfer the house to my father's name. Is this document valid enough to file a case against him. we have proof of depositing money to his account.