After going from 8.0 to 8.0.2, got the warning "NO Sim card installed." Tried hard resets, no luck. Decided to reset to factory defaults - bad move. Now I can't get past the "Hola" message on the first screen because if is now set up as a brand new iphone before restoring a backup. Now only solution is to go to AT&T store to get new sim card.
Also, I don't have a password for iCloud backup - therefore couldn't restore from there. What a mess. I am totally disappointed in Apple. After using their products for many, many years.