Currently I have 1 line at AT&T on contact. Im going to add 2 more lines on contract with 2 new iPhone 5s. But I only want to keep 1 new iPhone, and sell the other one. I assume new iPhone will come with new nano SIM card inside. So I'll have to unpack, get SIM out, before I sell it, right? And after I receive both phones, do I go to AT&T store to switch from iPhone5 to my old 3GS on newly added line and get micro SIM? Thank you in advance.