How does iPhone 4 choose roaming carriers?
When I visited with my iPhone 3G or 3GS, I was always roaming on Rogers network, by default (I made no preference changes whatsoever...just turn the phone on after stepping off the plane).
Now with my iPhone 4, same scenario...step off the plane, turn the phone on. In Vancouver, automatically latched onto Telus the whole time. In Toronto, Telus last night, Telus when I woke up, now in a coffee shop, and voilà, roaming on Bell...not once on Rogers.
I assume my roaming phone charges for voice calls will be the same (AT&T is my carrier and bills me, and says one rate for Canada roaming). But why the carrier-hopping? I'd think if it was signal, it would just shift cell sites, like it would on a single carrier.
Any ideas, techies?
Macbook Pro, Mac OS X (10.6.2)