Hi. I'm new to this forum so sorry if this has already been answered but I need to know. I have att right now with a pay-per-use data plan. I bought an iphone off ebay the other day and was planning on unlocking it. Well can att tell im using an iphone by the IMEI numbers that go through them every time i call or text? they do this now if i put my sim card in but is it different somehow when its unlocked??