Default [Q] Emergency Calls/No service issue at 2G

Hi Guys

lately i have upgraded my N4 from 4.3 to 4.4.2, i the network signal only shows one bar when working on 3G, when i switch to 2G a triangle occurs in the opposite side of the top screen and it says emergency calls only, in the status of the phone the received signal is 0 dbm and 99 ASU, I tried resetting my phone but it also have the same problem, also when i tried to select a network on 2G it didnot find any network.

please help is needed urgently......

thanks