Watch out for roaming charges when you travel!
"So how can you stop apps from using data in the background? With an iPhone, go to settings, then look under Cellular Data, and switch the data use to the OFF position."
https://abc7news.com/amp/technology/san-jose-family-billed-$13470-for-half-hour-of-iphone-internet/4072186/
https://abc7news.com/amp/technology/san-jose-family-billed-$13470-for-half-hour-of-iphone-internet/4072186/