Thanks. So, after explaining the unlocking/SIM process to my sister, she'd rather go w/ the AT&T passport plan. Hopefully her daughters will graciously accept not using streaming apps, just email. However, one daughter needs to use Whats App to communicate with a relative in Paris re meeting up. Would that use (a lot of) data on her phone (using AT&T plan not SIM card swap)?

Also, my sister will be driving in a rather remote area between tiny villages near the old East German border. She will have GPS in her rental car. Any chance that wouldn't cover a remote area?

Thanks so much!