Vodafone prepay. Oh, and another question, can these be used overseas if it gets unlocked?
My friend has an optus iphone and she said something about optus being able to unlock it free of charge, after to you spend $1000 worth of prepay credit with them (or something along those lines)
From what i recall. Iphone can be unlocked after 3months for free.. Or upfront for $80.. But You probably will have to get the person who bought it to get it unlocked as they may ask for the purchasers details etc. This was the same deal with an LG i bricked thanks to them screwing me around and wanting the "ORIGINAL" owner to contact them and get it unlocked.
if it's unopened, it shouldn't be locked to a network, as they usually do that at the shop upon purchase. you'd probably want to wipe it clean and install the latest software or jailbreak it anyway.