I had an iPhone 4 16Gb with model "mc608ll" that had been bought from at&t which recently had a problem and was replaced by the apple store. The replacement model that i got is "mc318ll". I did not activate this iphone in the apple store but instead came home and activated it on my laptop. I recently read somewhere that this is the model number (mc318ll) that apple uses as replacement iphone 4 all around the world, even with factory unlocked iphone 4. I was wondering if since this is the exact model used worldwide for replacement, that it may be factory unlocked and locked by apple store at the time of replacement, so is it possible that my iphone 4 is unlocked since I did not activate it in the Apple Store? Has anybody had such an experience or received this same model number in some other country other than US as unlocked?