FACE TIME on APPLE iPHONE:
If you have Face Time (Apple app) on your iPhone and a Wi-Fi signal, you can make free video calls. If your iPhone can run iOS 7.x, that version of Face Time also enables voice (ONLY) over internet calls to any cellular number. I use an iPod Touch, v5, running iOS 7.1. Face Time worked about 95 percent of the time on my Camino last year. That was before the voice only capability.
Unless your iPhone is a very early version, pre-iPhone 4, it HAS a SIM card tray on the side. Look for a pin dot sized hole. You need a special "tool" to pop the tray open - insert the "tool" to the hole gently and push slightly. I have heard that it can be done with the end of a safety pin too. Most iPhones and other smart phones use nano-SIM sized cards. So the slots / trays are VERY small, perhaps 1/4" wide @ 6 mm.
Without cellular service, the only thing you give up is on-the-fly texting and direct voice capability. But if you can use Face Time with Wi-Fi, you get video or voice only calls over Wi-Fi for FREE.
Finally, I always kept all my communications devices OFF until I reached my accommodation for the evening. On arrival, I turned the phone on for any incoming text messages. After dinner, I might call my family on Face Time or selectively check e-mail, etc. But, keeping up with people is not a priority.
Post an "out of office" or "on vacation" automatic reply message on your e-mail. Before you go, tell your regular correspondents that you will be away from regular e-mail from (date) to (date) and that during that period you may or may not check your e-mail. You might also change your voice mail greeting to let people know you are on extended travel and away from phone service.
You are on Camino. It's a pilgrimage. It is also a time to realize that nothing is really important outside the here and now. Once I returned and got back into all the electronic gadgetry, I realized just how special the quiet time on the Camino was. You will too. Enjoy it.
I hope this helps.