mobile

I was checking my phone to see if there was a way to Sim unlock the phone from the service menu and once I didn't find the menu needed I was about to exit the service menu. As I was exiting the service menu I believe I turned something on or off not. Now my phone Note 4 AT&T reboots over and over. Any ideas what could have change or what I need to do to correct the issue?

Thanks
Creed9090