Originally Posted by Monkeymo13
Currently a relative of mine has a S4 unlocked here in Canada, but it is the AT&T Variant (SGH-i337). His phone is rooted, but before I rooted, I tried updating through OTA to Kitkat but the Software Updater tells me there are no available updates. I've also tried connecting it to Kies but it tells me to update via OTA. How can I update his phone to Kitkat? He's currently on Rogers Wireless and is currently using Android 4.3. Also once I update it, is there a way to root it again without tripping knox or voiding the warranty?
Read the return to stock section of All things ATT
There are 2 versions of kitkat. One that ends with NB1 and the other is NC1 (newer).
If you want to get to NC1, you will have to flash NB1 first (or update to NB1) and then update to NC1.
There are 2 firmware versions for NB1 - one is rootable and other is not (but can be updated to NC1 and then rooted).
You would root it using towelroot (just google for this).
-- This post of mine will tell you how to update from MK2 to NB1.