My little brother just took delivery of his 2nd hand Iphone 3g (MB Model) which is running 4.0, jailbroken and unlocked. Like most 3g iphones, 4.0 is running SUPER slow and he asked me about upgrading to the new 4.1. He isnt bothered about loosing the jailbreak BUT he/nor me are sure what the default carrier is for his phone. I'm aware that there are no jailbreaks or unlocks currently for 4.1 and the last thing he wants is to upgrade to 4.1 and his 'O2' no longer works. Is there anyway to find out what network the iphone was originally factory locked to?? (before it was jailbroken and unlocked)? Thanks.