OP brings up an interesting issue of alternative phone access should cell service not be available? Personally, I'm a stickler for backups, and use Verizon mobile as primary, and keep a minimal account on different smartphone with AT&T.
If you can find internet access for laptop or tablet, you can use Google Voice account to make and receive free calls (VoIP) in U.S. This is what I do when teleworking, in that I make or take my calls from my computer when I'm working. Call my office or cell phone number, and it conveniently rings on my PC.