can i use my old o2 sim in the iphone

[usingautumn]

has anyone had any luck with their existing AT&T card in the iphone, or will I need to unlock to use my existing o2 contract?

thanks.

 

[roblawton]

You will need to unlock to use any other SIM card than the one already in there.

 

[footandmaff]

I'm planning on getting an iPhone at some point in the very near future, and I'm sure this question has probably been asked a few times but here goes... If I purchase an iPhone in the UK which is locked to O2 and I use an O2 sim in there then will it work? I understand that when I purchase the phone I essentially purchase a brick until the activation process is complete but there have been workarounds for the activation process on 1.1.1 and I imagine that it'll be the case in a while for 1.1.2. So if I manage to activate the iPhone through a workaround is it likely that I'll be able to use an O2 sim without going through the unlock procedure (i.e. using my existing O2 sim without signing up for a new contract)?