Breaking off an Engagement

I am 30 years old woman. I have got engaged on 24th of Feb with a relative of my family. They are continuously postponing the marriage dates saying untrustful reasons. Now the person I am engaged said during on a phone conversation that he is serious alcoholic and had issues with a girl at his office and that he removed his Facebook profile, gmail accounts and also changed his phone number 2 months earlier engagement. From then on he is not answering the phone or when he answers he says that he is very busy. Then my family got involved and asked for his payslips and other proofs as to his employent and education. Then their parents are saying the marriage is based on trust, since you are not trusting our son their ego got hurt and are cancelling the marriage scheduled in August. They are also saying that i would pay price for asking such details. They will endanger my reputation in the public and make sure I will never get married. They had given us a gold chain as surity along with ring, now they are asking to give them back. Now my elder sister and brother in law are asking them to promise on a bond paper they dont cause any trouble for furtherance of my marriage they we give back your chain and ring. They are not accepting it. What can I do in these situation. They are spreading rumours about me in my relatives.