Thanks for all your feedback. I booked a written complaint with Reliance and they forwarded the same to LG. One Executive from LG called me and understood the problem and advised to give the handset to service centre. Service centre advised to replace the PCB, but I have not accepted, since the originality goes away. Then LG people agreed and arranged for a new replacement.
The people at LG,Chennai and Reliance Webworld, Adyar,Chennai are so polite and their action is to be appreciated.