How to Unroot AT&T Galaxy S5 with SafeStrap Recovery Backup!
Since currently (as of writing this post) there’s no stock firmware available for AT&T Galaxy S5, you can use a SafeStrap Recovery backup to restore your AT&T Galaxy S5 SM-G900A. Now, this is the Android 4.4.2 ND3 firmware, it will only work if you have not upgraded your bootloader past ND3 most likely.