Honestly, that's nothing compared to what an AT&T rep told me when I was opening my father his AT&T account [He lives outside the US and travels and doesn't have a SS].
So, anyway, I asked the AT&T rep what AT&T thought about unlocked iPhone and he told me, AT&T doesn't really care, thing is, once something goes wrong with the phone they can't really do anything cause they have to be AT&T activated for warranty to kick in. He later went on to tell me that he has unlocked his friend's iPhones and that if you really want an iPhone outside AT&T go for it as it is a marvelous device [at this time I noticed he had an iPhone].
AT&T rep said that he unlocked his for abroad travel since he thinks AT&T's roaming charges are absurd.
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Pretty much what you wouldn't expect from AT&T rep, but hey, its a free world
those were his $0.02 and also my $0.02 has I also use AT&T and I unlocked it just to use anywhere.