If iphone is BNIB on a different network can i insert my sim card before syncing to itunes to unlock (not jailbreak).

Question

I am looking at buying an iPhone from eBay as my O2 contract is pretty good and I don't want to lose this. I read somewhere that a Brand new in box iPhone is sim unlocked already even though it was from a vodafone or 3 contract. So as long as I put my current sim in before I sync to iTunes all should work smoothly. But it does need to be BNIB as an unwanted upgrade from the carrier.
The reasons I am looking to do this is mainly down to:
1) my contract being unlimited data allowance which 2 different people from O2 have told me that I can use with my new iPad 2 wifi with the portable hotspot app.
2) If I buy an iPhone through O2 I will lose my current contract and still pay a good £300+ for a new iPhone 4 and be stuck with a 1gb data limit. (Last month I used 3gb).
Any help lads / lasses?

Answer 1

I read somewhere that a Brand new in box iPhone is sim unlocked already even though it was from a vodafone or 3 contract.
That is incorrect. iPhones sold by the carrier are, except in countries where locking is illegal or otherwise not done, locked to the carrier. The carrier may offer unlocking services, but often only for the original contract holder. I would strongly suggest caution when considering this iPhone or any from eBay; it's highly likely that is was jailbroken to unlock it (making it not "new in the box") and would lock back to the original carrier when the OS is upgraded or restored.
If you want an unlocked iPhone, the safest route is to purchase from Apple, which is to the best of my knowledge the only official source for unlocked iPhones in the UK.
Regards.