Like walkie-talkies. Phones only work as communication devices in vicinity of the network towers.
The only thing is there's no encryption on amateur radio.
Whatever (text messaging on a HAM band) you want to use, there is not a qwerty (or touchscreen) device that you can use to compose those messages.
You either need to connect a computer to such a device or (I think) there are one or two handheld radios that you can type out messages using multi-tap.[1]
It's worked really well and I've abused the unlimited plan chatting with a few close people while lonely in the woods.