Landlord refusing to return the security deposit

I recently moved to navi mumbai for job and i rented a pg room. Me and my roomates paid around 5.5k as deposit(500 was for police verification the certificate upon asking repeatedly was never shown). The landlord had certain rules, which was the agreement and we had to sign it and the points say that we are supposed to stay for more than 3 months and we have give exactly one month notice period for the vacation of the pg ( exactly one month not one day before or after). this being i received a transfer on feb 1st and we always pay the rent on the 13th for that month so i wanted to vacate before feb 13th. From that time on i started calling him and pestering about deposit for which he didnt respond well. the rules say we have to drop a mail that we are vacating exactly one month before. the transfer was a sudden news and i was ot aware of this. although in december we had the idea of vacating this PG soon based on our job. so we sent out a mail on dec 13th saying we will be vacating on jan 13th. but however we didnt. we didnt do the same procedure on jan13th. but we have given him 2 months notice period to tell. now when i call him he says yolu havent followed the rules on agreement and i cannot give you the money. if i say, i will send mail now give money in one month he says no. we are small time middle class family. He has just ate our whole 5k and for students who have begun to work now it is a big deal. and he is not agreeing for any other methods just cos i didnt drop a mail on jan 13th. this issue has been faced by most of the girls in that pg as we dont know when we will get our transfers and all so we cant inform him one month prior. maybe it is a trick paid by him knowing all this. one girl went and gave police complaint but that went in vain as that landlord has influence and he himself is a lawyer and so the police told her to leave the matter just like that. i have vacated the pg now and left the city but i keep calling him and most times he doesnt pick and when he picks he tells you didnt follow the agreement. please help me