I have a 3GS in black but now wish I had gotten it in white. My sister was going to order one in black as well but if she orders one in white instead could we just swap phones and SIM cards? That way I get her white one and she gets my black one. By swapping the SIM cards AT&T would see her white one as mine and my black one as hers, correct? Is it that simple or is it more involved than that? Would she activate the white one before swapping the SIM cards? Thanks!