I'll be getting a full price, unlocked (T-Mobile if there is no sim-free model) iPhone 6 on launch day, and will be traveling to France shortly after. What is the cheapest way to get a data only sim card to use for a little over a week while I am there? I'm on an AT&T mobile share plan in the US with a few other family members, and I'm sure they'd love to charge me tons for using AT&T while I'm there, assuming there is even roaming service.