I'm in the beginning stages of planning a month long trip across the United States, starting from Detroit or Buffalo and heading west. I have an unlocked iPhone 5 and would probably end up using ~1 GB of data and ~100 min of talk time. Since I live in Canada, I have no idea which US provider would offer the best pricing and more importantly, coverage across the country. I am looking to visit many of the prominent national parks and other nature oriented destinations in Colorado, New Mexico, Arizona, Utah, Nevada, California, Oregon, Washington... The itinerary is not yet set at all, but it will be roughly like this: I see that most prominent ones are Verizon and AT&T, but I think Verizon is CDMA and won't work with my GSM iPhone. What kind of coverage can I expect from AT&T outside of major cities (for example, in national parks, forests and preserves), and are there other providers that have good coverage across the country? What should I know about rate calculation, for example, if I get the SIM card in Michigan, will I be charged long distance rates for making a call to a Utah number while in Utah?