Re: Will an unlocked Verizon Galaxy S4 work on AT&T network?
Just like the Note 2, DNA, Blackberry Z10, and the other slew of the latest Verizon smartphones, yes it will work.
You will get voice (talk and text) and the equivalent of "3G" internet speeds for data.
Data might not work out of the box. (It didn't on the Note 2 and did on the Droid DNA)
To fix this, you just need to add AT&T's or the carrier of your choice's APN settings. This requires root and a simple edit of the APN file using a text editor then replacing it using Root Explorer. XDA has the full tutorial which takes literally 5 minutes to do.
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Also wanted to add, no LTE. Verizon and AT&T use different LTE bands and there is no way LTE will work.