Sony India — sony tv 42 inch not working

I bought sony led tv 2 yrs ago, few days before it suddenly stopped displaying picture. One of the service person came and took tv motherboard with him for checking. Today he came with new motherboard saying that my old motherboard was faulty. After he installed the new motherboard he brought with him and went.. After 5 to 10 mins my tv display was blank again. I asked sony customer care and service centre about the problem and also the cost of motherboard but they were not properly responding. It was really a headache for me, as they arent providing me suitable service. Please do the needful.
I want to know the price of motherboard.

Regards.