Thankfully, I have not had to try this but I'm told that even a cell phone that is fully charged but not connected to a service can be used to summon help. I find my current phone too "clunky" to keep with me at all times but my old flip phone is small enough to be acceptable in a pocket. I'm told that I'd have to be able to tell 911 my name and location. I think this was the way those mistreated children were finally able to get attention not long ago. Donated phones are sometimes passed along to women in potentially abusive situations so they have a way to get help. They don't have to have cell service but can still get help.