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I think I figured it out. I can't get the switch to show up at all on my T-Mobile phone. Whether I fill the info in or not.

On my wife's AT&T phone, the switch is there right away. So it seems the issue is checking AT&T on a non AT&T SIM card.
 
It doesn't matter what the screenshot on #21 looks like. That's not what shows up on my iPhone. I'm going for Space Gray anyway, so the extra 10 seconds won't kill me.
 
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