Data roaming is a feature on an iPhone that allows you to use the internet, send texts, and make/receive calls in locations where your primary network carrier doesnt offer coverage. It permits internet access over a cellular data network when youre in a region not covered by your carriers network. When you enter an area where international data roaming is available, youll usually receive a text message explaining the cost of using data, making calls, and sending texts.

Data roaming can be convenient if youre outside of your home network and need to access the internet, but it can be a costly addition to your monthly cell phone bill. If you want to make sure that you dont use it, the best thing to do is to disable it altogether. Disabling this option keeps your phone from connecting to data networks outside of your home network. If youre ever outside your home network and need access to the internet, you can always turn this option back on, but at least youll be prepared for the charges youre incurring.

To turn data roaming on or off on your iPhone, go to Settings > Cellular > Cellular Data Options, and toggle Data Roaming on (green) if you want to enable it or off (gray) if you want to disable it.