Update to marshmallow using ATT device on cricket (att)

[eddiekeyton]

So I have read that marshmallow is out through att for the m8. I checked for updates because I am on lollipop and it said no updates available.

I'm using the att m8 on the cricket network. Cricket uses att towers but technically its not att. How do I update a non rooted device that isn't being used on the network it was intended.