If you have a radio to call people, will they also have the same frequency band and be waiting for you to call at the time you want to call them?

A friend of mine used to have a satellite phone. If you really wanted to call someone, that might make more sense, although they are not cheap. My friend bought it because he owned his own airplane and he used the phone to download radar images of bad weather when he was in his plane. But when we were on a kayak trip and out of range of cell phone service, he used the sat phone to call his voice mail.

If you anticipate occasionally being in places with wifi, set up your smartphone first with a VOIP phone service assuming you have such a phone. I use Google Voice and Hangouts and Hangouts Dialer to make phone calls when I have wifi.