Search "Rumspringa". When Amish kids hit their teens the community basically unleashes them, to allow them to get a taste of the outside world and decide on their own whether or not they want to live by the community and church rules. They get cellphones, cars, cable TV, video games, have big loud drunk parties, etc. See the documentary "Devil's Playground" for a look into this part of the Amish world.
Granted the people involved here are a bit outside the Rumspringa age group, so it may also be that some communities have gotten looser about phones in the past 10 years.
See also "Ordnung". The Amish can pretty much use whatever technology the local elders determine is non-disruptive to the community, although some restrictions are placed on how and when such things can be used (e.g., phone outside the house, power tools that run on compressed air, etc.).
Travel to Amish country sometime; you'll see Amish girls hanging out with non-Amish boys, Amish men and women working at stores where they have to run the computer registers, and so on. The Amish don't resist technology out of superstitious fear; they're just real careful about what serves them well and what does not.