My brother bought an iphone 3gs from ebay, when plugging it into the pc it says activation need, i had an old iphone n it was easy to get past the activation back then, however it doesnt seem so easy now.

i dont know know what firmware he is on however by looking at the serial i can tell its old boot

my question is this, can i activate it by using an o2 PAYG sim?? or if needed i have a friend who got an iphone 3gs yesterday from o2 could i just pop his sim into the iphone n connect to itunes and activate it that way??