Sony — DEFECTIVE CAMERA

I purchased “SONY” Cybershot Model DSC S650 purchased on 1st November, 2007 and in July, 2008 onwards it is not working. Seller not ready to repair or replace. original bill & warranty card retained by the seller when handed over the camera for repair and now they refused to give and not attending phone as they are in Mumbai.
Talked to sony india and they refused to attend compalin in absence of bill & warranty card.
I spent rs, 7800/- for purchase of above camera. Now I lost everything neither camera nor money.
What is to do, please help