I, too, have an iPhone 5 and I purchased the Nexus 4 only for a project (it's a nice phone, but I will be selling it soon). When I inserted my micro sim using an adapter, I was only getting cell service. So, I went to AT&T's online chat and the guy told me that they needed to activate the data. He had me turn the phone off, did something on his end, and then it worked. The process seems more complicated than it needs to be, but he said whenever I want to go back to my iPhone, I needed to talk to them again in order to transfer the data.