I just Googled AT Trail Cell Phone Coverage and here is 1 of many Blogs/forums.
https://sectionhiker.com/appalachian-trail-cell-phone-guide/
I doubt you find anyone on this LP Forum that has hiked with a phone in the last 2 years, more than a few sections. Maybe talk to the hikers and read the forums pertaining to the AT Trail.
You don't even mention what section you are hiking?
This is a travel forum, not a hiking forum.