Walked CF last year, starting at SJPP. Intended to get a SIM card for the data rather than the phone as I had a tablet, and then more to keep in touch with family via social media than by phone. I had not planned on booking accommodation ahead and I had an app on the tablet which showed the path of the CF on satellite image for navigation purposes. This app did not require phone access and got me out of trouble a couple of times when I strayed from the path I wanted.
Tried getting a SIM card in SJPP - the Orange shop "could get one sent in in about three days..." - a phone card was readily available but not a phone/data card. Unfortunately, not much use to me as I was leaving the next day.
As matters turned out, I found that almost every albergue I stopped at had free wifi - the only issues I had were no wifi or limited bandwidth at some municipal/faith-based establishments - the world continued to spin on its axis despite this. In addition, many bars also advertised free wifi. I managed to keep a current log of my travels on social media for the information/amusement of the folks at home.
Doing it all again in 2018? - I would be more inclined to get a phone/data card in Paris on way to SJPP to facilitate booking accomodation ahead, although booking ahead every night seems to be a bit excessive. Plan B - get one in Pamplona (as many on this forum have suggested).
That said - walking unplugged is not life threatening and for some can be an invaluable part of the camino experience (learning what you can really do without, and dealing with each days' challenges as they arise).