I understand that downgrading an iPhone from 1.1.1 to 1.0.2 will enable the process of jailbreaking. What if I downgraded a brand new iPhone with 1.1.1 out of the box(never unlocked) to 1.0.2 and went through this process of using ANY AT&T SIM:

http://www.hacktheiphone.com/iphone_...r_windows.html (On this page, see Step 13 and down)

Correct me if I'm wrong, but this is not unlocking and it just 'tricks' the iPhone into thinking that the new AT&T SIM was the original preinstalled AT&T SIM card. It seems like I would be able to use my calling & sms features again but I'm just concerned it might conflict with the updated modem. Any opinions? Thanks!