Chandu, try reset the network settings with sim ejected and wait till phone says no sim then insert again. Usually that should fix the issues if it has a sim pin also.
If stuck in iTunes, do you know if it is displaying the baseband information etc? Or is that blank? If it's blank, the only thing I could suggest is to restore the device once more, otherwise try a reflow of the chip itself if your comfortable with the idea, or get someone who you trust with electronics to do for you.