So, I had tryed to install at root and flash a Rom onto my Samsung Galaxy s4 i337 using MF3. I was running Android 4.2.2 and when I had tried to unroot my device, something happened and I wasn't able to FULLY get the root off my device. A couple days ago, I had wanted to upgrade to the Android KitKat 4.4 so when I completed the process. It went into Download mode, and then just crashed. Right now it shows an error message saying
"System software not authorized by AT&T has been found on my phone. Please turn off your phone and go to the nearest AT&T store for help."
Also in the top left hand corner it says Secure fail:Kernel so obviously it means I am missing a Kernel of some sort.
Please help me!