Originally Posted by D582

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.