I got a replacement iphone from the Apple store on monday (MC319LL). I tried a non-AT&T sim that I use at work for testing and it did not say "invalid SIM". When I put the same test SIM in a AT&T Q9h, I get a screen that says "unlock code required". Therefore I am fairly confidant that the test SIM is non-AT&T. From this, can I deduce that my replacement iPhone is unlocked? Is there any other way to tell?