Unhappy [Q] help semi bricked Samsung galaxy s4 i337

okay so i had my Samsung galaxy s4 i337 4.4.2 running fine with root and superuser installed but i tried to install a custom recovery i cant link at the moment
i did this using recovery tools now i'm getting a message when my phone starts up with a big exclamation mark saying software not authorized by at&t has been found on your phone is there any way to fix this please help me i don't care if i loose root access or anything i just need/ want my phone to work again
EDIT i attempted to flash it using Odin back to stock but that failed now i get the message firmware upgrade encountered an issue please select recovery mode in kies and try again when i try to upgrade the firmware in kies it say this devices firmware cannot be upgraded
p.s. Knox warranty void is at the value 0x1