My Galaxy S20 works perfectly everywhere I have been including San juan and Rio grande. My wife's iPhone 12 has not worked since we landed. Tried a bunch of setting changes and still no service. Both phones are on the same exact plan.
Let's get her connected, Pittraveler. Please make sure that she switches her WiFi to the OFF position in her iPhone. Then, have her turn the phone off for 2-3 minutes, and then turn it back on. Ensure that her WiFi remains off. WiFi will generally block iPhones from making their initial network connection. After a few minutes, she should be connected. Let us know if this helps. Once connected to the local network, she can turn WiFi back on if she likes. - Henry