In my case, I had earlier set up the T-Satellite beta using the second eSIM slot on my phone, and turned off the primary service (AT&T) in order to test just T-Mobile's feature.

Even 120 miles from town in a cellular dead zone, I was able to stay in contact with my family using the $10-a-month T-Satellite service. And I didn't need to be on a T-Mobile plan or buy a new ...