LG G3 ( AT&T) restarting When SIM Inside

I have LG G3 AT&T phone working very well for 6 months on any SIM card .
Suddenly phone restarting itself ,
so I reset factory setting and format data ,
But problem still not solved ,
Then I removed SIM card and check phone and phone working great without SIM ,
Whenever I insert SIMcard phone being restarted in few seconds .
I tried to check unlocking code check method
This phone is permanently Locked and can’t be unlocked .
What opration should I perform throw OCtopus LG box .
Phone firmware 4.4.2