How can I legally get back this property into my name.

Hello Sir / Madam, I'm very thank full to all the respected lawyers who contribute their knowledge through this website. I am working in abroad [Age - 40 Years] & married . I am having three sisters married & settled. I given power of attorney to my father, for operating my NRE bank account in order to purchase a land in Chennai. With that money , my father [ 71 Years] purchased a land in Chennai & registered in his name in the year 2011 . He promised me that when I come to India, he will transfer the property to my name. Now, when i am asking him to register the land on my name, he is not agreeing & refusing. But, he registered a WILL in my name, & given the original WILL document to me. The WILL states, that after his life time, i can transfer the property to my name. Now, my father threatens me by saying that , he will cancel the registered WILL at any time. In this situation, my three sisters jointly given a NO OBJECTION DOCUMENT through a Notary Public lawyer for me on 2015 . The above document states, that I purchased & registered the above land in my father’s name and they have no rights on that property in future. I have all the bank transaction details, as a proof for the money withdrawn from my NRE account , by my father for purchasing the land & copy of the Power of Attorney letter submitted to the bank, signed by both of us. He has no income at all. So, please advise me how to proceed in this matter and how can I legally get back this property into my name, if my father cancels the registered WILL? With Many Thanks Balamurugan.S