Can't update Samsung Galaxy S4
I am running the stock 4.2.2 ROM. I have never been able to update, either OTA or otherwise. The update downloads, the phone reboots, and there's an installation progress bar. It gets to about 25% and the phone spontaneously reboots, displaying a message that the update could not be completed. I tried updating via Kies on my Windows computer, but Kies claims that my phone is running the latest firmware, when it's clearly not.
In the past, I had an AT&T representative attempt to push the update to my phone, and they were unsuccessful. What can I do? I would like to update my phone, but I'm running out of options.