Ok you actually made me curious so I threw in a quick search, turns out they aren't opposed to technology or electricity per se at all, it's a much more philosophical stance about being connected to / dependant on the outside world. And it's indeed different for every community/parish to what degree it is allowed, some more conservative groups still don't use it all.

Some Amish, though not all, also accept the use of solar panels to generate energy to charge batteries, power an electric fence for livestock, or heat water. Donald Kraybill has called this form of electricity tapping into “God’s grid”. [...]

The Amish are not against use of electric power and acknowledge its usefulness. They seek to remain off the public grid in order to prevent worldly influences from entering the home, and as a symbolic means of remaining separate from the world.

At the same time, they see value in limited use of electric power, and thus generate it by various means, making use of diesel generators, batteries, inverters, and solar panels, among other technologies.

https://amishamerica.com/do-amish-use-electricity/

There are still some extremely conservative orders (also called "low" orders or "old" orders) of Amish that still do not allow the use of batteries either in the home or as safety lights on buggies. [...]

As history marched on, and new inventions were discovered and marketed, lines had to be drawn as to what was, and what was not acceptable within the Amish church. The acceptance of electricity within the home was one of these lines. By the 1920's most Amish churches had agreed on a ban for Amish church members being allowed to connect to the electrical grid. [...]

Today, most Amish churches forbid the use of public electricity because it is seen as a "connection to the world" but batteries allow many Amish families and businesses a limited connection to power and the ability to run such items as calculators, alarm clocks, cash registers, drills, electric fences, and even cell phones without discipline form their local Bishop.

http://www.amishcountryalmanac.com/2014/02/batteries-and-amish.html

Now please don't ask me how they rationalise buying generators and fuel as not being dependant on the outside world, because I don't have the slightest clue.

Gasoline powered generators apparently, and then the big batteries charged on those can charge the phones or power whatever they need. But again, this is different from community to community as far as I understood it.