You are 100% correct. While it may be the law, it is apparently not followed every single time. I had no issue with showing my passport had I been asked.

One option we use is to forward both of our cellphones to Google Voice. That way we don't have any incoming calls ring through. However, Google Voice sends us a text (when we have wifi) with a pretty good transcription of the message. That way we do get the messages from our next lodgings that were booked with our US cellphones. And we can text or email or call if necessary.

You can of course install Google Hangouts on your phone and enable incoming calls, so when someone calls your Google Voice number (or your cell numbers that get forwarded to Google Voice), you can just answer the calls in Hangouts. But yes, the Google voicemail is handy, too, and you can listen to your Google voicemail messages in the Google Voice app, even if just on WiFi with no SIM or cell service. But buy a SIM card and then you can receive those incoming calls from your cell phone forwarded via Google Voice anywhere (in Hangouts).