Owner not returning Security Deposit

Hello, I stay at Navi Mumbai. I intend to vacate my rented flat on 28 August 2015. I had also written a letter of notice and handed it over to my owner on 28 July 2015. I was not at work. So my father met him and handed the notice but he refused to take the written notice and said very sweet things to my father that we are very good tenants and there is no need to give the written notice and that we have put him in tension now for arranging new tenant and deposit money. Now when we have found the new flat, I just called my owner to inform the same that I shall be vacating the flat on 28th August 2015 as said earlier..In that case I requested him to arrange the deposit money(which is Rs.50000) that he needs to return. He started saying that we should stay for another month or two since this is a rainy season and it is very difficult for him to get new tenant. When he gets one , he will return the deposit money. On telling him that its not possible, he said he will try to return 30000 by 28th August and give the remaining 20000 by the 10 September 2015. I am really worried as I have to pay the security deposit to my next owner and I am not so well -off to arrange the same from elsewhere. I live with my parents in Navi Mumbai. Kindly note that our agreement was not a registered one, but it was a notaried agreement and its clearly written that I have to give the notice in writing which he refused to take. Also, out of all his tenants I am the only tenant giving the rent and paying the electricity bill regularly. Very worried.. Please suggest a remedy for this. Thank you.