For almost everyone, it's a good idea to leave Cellular Data on. ... When Cellular Data is off and you're not connected to Wi-Fi, you can only use your iPhone to make phone calls and send text messages (but not iMessages, which use data). It's amazing that almost everything we do on our iPhones uses data!

What happens when I turn cellular data off?

(On iPhone, tap the “Settings” icon, tap “Cellular,” then turn off “Cellular Data.” On Android, tap the “Settings” icon, tap “Network & internet,” tap “Mobile network” and turn off “Mobile data.”) After turning off mobile data, you'll still be able to make and receive phone calls and get text messages.

What does turning cellular data on do?

Mobile data allows your phone to access the Internet even when you're not on Wi-Fi. Mobile data gives you an Internet connection anywhere as long as you're connected to a cellular network.