Help Update unlocked phone?

[Stingroo]

So I have an unlocked Galaxy S4, that came from AT&T.

It's horribly out of date. Still running Android 4.2.2. I notice that it keeps randomly rebooting itself lately, so I'm thinking the old software is to blame.

But when I go to update via settings, it tries the AT&T update utility, which is all fine and good... except it doesn't have AT&T service so nothing happens.

What do I do here?

If it helps, it has a Metro/T-mobile SIM in it.

 

[Stingroo]

TTT

Anyone?

Also, if it matters, I am rooted. Would be happy with loading a ROM that was stock minus bloatware.

 

[sreum]

I would go check out or post this in one of the all things rooted forums.

You might have better luck with a response.