What can I do if landlord is not returning security deposit?

I was being shifted to the PG for 2 months for my exams. There was a girl who has tortured me and even given me a life threat. I informed all this to the PG owner and decided to move out. He continues denied to pay the deposit amount and after visiting to the police station he paid me less than half amount of deposit. He have deducted the amounts by making new rules. He is running the PG without being registered and I feel there are many suspicious things are engaged in his other PG.