Custom Open Padlock Icon Hell, Help Me

[ThaDaedalus82]

My note 3 started showing the custom open padlock icon at startup and I cant connect to my mobile network to use my data. I definitely did not try rooting it or anything of the sort. I tried the reboot in recovery mode and have had no luck. this is getting frustrating bc I dont know **** about phones. The at&t service rep had no clue how to help. I am so frustrated that Im almost willing to factory reset but I really dont want to. What is going on and why on earth did this happen if I didnt try rooting?

 

[ThaDaedalus82]

Well...I did a factory reset and that custom screen is still there. How is that possible? I still can't connect to my mobile network or make phone calls.