Car owner is not providing needed document for car transfer

I have bought a car 2years back and paid whole amount online in 1 go. I have form 29 and form 30 signed copy form owner and I also have payment receipt with signed by owner. when I tried to get it transfer on my name I came to know that car had loan but it was cleared. I contacted owner for bank loan NOC and kept her chasing for more than 1 year. In the end owner gave me expired NOC which is of no use now. Now when I want to contact her she is not receiving my calls and she is threatening me that he ll file a case of harassment. I am real genuine buyer and I don't want to indulge in any issue but owner is not helping me at all. I am totally helpless as I can't sell the car to anyone as it is not on my name. Please suggest what can be done here.