Does ANYONE know

[rgch999]

the answer to my query.
I have a 3gs phone that was purchased outright and jailbroken and unlocked with ultra snow, on 3.0.1.when I received it. I am completely ignorant as to how the activation works but have used I tunes to sync and everything is working perfectly.
IF I upgraded to 3.1 [yes I know I would lose my jb and unlock)could I put in an O2 pay as you go sim card and would it allow me to activate on O2 payg, or would it say that my phone has already been activated previously with a different sim and basically brick my phone.
Simply speaking how does Ultra snow affect the activation process if I want to return the phone to a legitimate O2 pay as you go state. The sim card i propse to use is one of the ones designed to give unlimited wifi and browsing that I believe is supplied with new i phones purchased on payg. It wasnt supplied with the phone as the phone had been jb and unlocked when i received it.
Despite previous requests no one seems to be able to give me a simple answer. Any takers from those in the know.

[macabre]

I just thought the initial activation with itunes could be done with any o2 sim card and then when activated you could use any sim in the phone. i activated with my mates 02 contract sim then used the phone with 3 or 4 different sim with no adverse effects.

[rgch999]

Thing is Im not sure how the process works. I purchased the phone new but jb and unlocked, but does that mean that the person who did the jailbreak activated the phone or did I do it once I logged into I tunes.The Apple site shows my phone as an O2 ohone although in fact I am using a different sim at present. However I am thinking of going back to O2 and was wondering if it was simply a matter of putting in an O2 sim and synching with I tunes, or whether this would start the alarm bells at Apple and lock my phone up.

PS The O2 sim card is a payg and has not yet been registered/activated. I assume I have to register it with O2 before it would work in any phone. Should I register it in the I phone or any phone just to activate the sim card. Im afraid all these technical details are a bit beyond me!!!!!!!