So I recently got my first Android phone from the AT&T store last weekend and I absolutely love it. In a week, I'll be starting school and this year I'll be having PE. During my freshman year, both my phone and iTouch were stolen from my locker. I'd love to keep my Galaxy S4, so I was planning on SIM swapping to the iPhone 4S for days I have PE. So I asked the salesman at the store if I could swap between phones, and unfortunately he said no. However, it's possible that he misinterpreted my question as if I could use my iPhone 4S SIM card in my GS4. So I've been searching all over but I can't get a definite answer. Some say it's safe and others say AT&T impose fees or something. I could really use a response before school starts.