Well… some Amish have permission to use them strictly for work purposes (they are allowed to use tech if they’re working for someone English to the extent required). And some have phones strictly for true emergencies. But yeah, by and large they shouldn’t.
If they’re in rumspringa age range they likely will have to turn over the phone and get a scolding, but it’s not like Amish kids aren’t caught with phones.
Anyone post-baptism in the church may face community discipline but I doubt anyone it going to get kicked out for this transgression. Amish aren’t saints and people make mistakes on a regular basis.
That’s a much more serious problem. Sucks to be them. But then, if convicts could stay out of trouble they might not have been convicted.
Much more serious are folks at risk of harm from abusers.