Fraud by coaching institute now refusing to refund. What should I do?

Dear sir, I joined an institute for civil service coaching. I paid 70,000? for prelims and mains together. The coaching was below standard and students were taking classes. No proper faculties were there and no facilities as promised were given. Not even materials were provided. When I spoke to the owner regarding the drawbacks I received mental harassment and he is adamant for not giving back the refund. I can't afford to join a better institute also. Around 10-15 people who Complained faced the same mental torture and they all stopped going to the institute. Can I give a joint/ individual petition against this man so that he won't repeat this with any other student? I need help.