Originally Posted by
TGarza
AT&T carrier unlocked your iPhone. We had a similar problem with one iPhone not sending texts in Vancouver with tier 2 tech pushing the change to the phones. Carrier unlocking is the only method to manually select the carrier. All US cell companies except for Verizon will carrier lock the phones sold.
SIM locks on the phone have nothing to do with the visibility of the Carrier Selection menu. It is controlled by provisioning made to the SIM/phone by the carrier itself. This concept goes back to the GSM days.
My US iPhone is on AT&T, and I can assure you it is very much locked to AT&T. However I have the carrier selection menu visible at all times, even in the US, because AT&T enabled it for me. This carried over when I upgraded my phone and moved the SIM card across. If I put a different AT&T SIM in the phone the menu disappears.