Default [Q] HELP regarding lenovo p780 network.

Hi everyone,
This is my first post/question on this awesome community. I have a lenovo p780 8gb, the phone was working absolutely fine until yesterday. Now I am not getting any signal coverage whether it be 2g or 3g, I didn't do anything to the phone, no root, no physical damage etc. I tried searching for a solution but all effort in vain. I checked with different sim cards, tried the factory reset but the signal never came. I also tried to upgrade the firmware but after downloading the update data of 11gb the phone entered recovery mode and the update failed. I will post the complete error message if any one asks. Please help, it's very very annoying.
thanks