No GSM/Edge Connectivity .

We had a few hours network outage due to security reasons. But my G3 didnt recover when the outage was over and is still stuck at "no Service" even after several reboots, clean flash of cloudy and restoration to stock using nandroid. It was working just fine a night before. I have tried restoring Stock from nandroid but still no luck. I have tried different SIM cards too but still no connectivity.

*#06# shows proper IMEI number.
Baseband was shown as Unknown, So I flashed one from xda threads for D850 V10D. Now my Baseband is known. But no luck.
Wifi works fine.
Bluetooth works fine.
Sim Toolkit works fine
SIM contacts are visible
AAT tests USIM1 Passes

I am back to Stock using TOT method.
I even had a bit of luck and caught some signals last night but they came and Whooosh gone again never to return.

It is to be known that I am in Pakistan and D850 is ATT US. Do I need to take care of any unlocking to make it work here that the shopkeeper may already have done before selling it to me ? Because it worked fine before.
Edit::
I checked for unlock code. my phone says "Phone is not personalized". So i guess I am not operator locked.
Previously I had posted this in "G3 troubleshooting" forum assuming it to be cloudy ROM related but I think its much more serious than that. So posting it here in D850 Forum.