Use Cellular settings to turn cellular data and roaming on or off, set which apps and services use cellular data, see call time and cellular data usage, and set other cellular options.
If iPhone is connected to the Internet via the cellular data network, the LTE, 4G, 3G, E, or GPRS icon appears in the status bar.
LTE, 4G, and 3G service on GSM cellular networks support simultaneous voice and data communications. For all other cellular connections, you can’t use Internet services while you’re talking on the phone unless iPhone also has a Wi-Fi connection to the Internet. Depending on your network connection, you may not be able to receive calls while iPhone transfers data over the cellular network—when downloading a webpage, for example.
GSM networks: On an EDGE or GPRS connection, incoming calls may go directly to voicemail during data transfers. For incoming calls that you answer, data transfers are paused.
CDMA networks: On EV-DO connections, data transfers are paused when you answer incoming calls. On 1xRTT connections, incoming calls may go directly to voicemail during data transfers. For incoming calls that you answer, data transfers are paused.
Data transfer resumes when you end the call.
If Cellular Data is off, all data services use only Wi-Fi—including email, web browsing, push notifications, and other services.
Turn Cellular Data on or off. Go to Settings > Cellular, then tap Cellular Data. The following options may also be available:
Turn Data Roaming on or off: Data Roaming permits Internet access over a cellular data network when you’re in an area not covered by your carrier’s network. When you’re traveling, you can turn off Data Roaming to avoid roaming charges.
Enable or disable 4G/LTE (varies by carrier): Using 4G or LTE loads Internet data faster in some cases, but may decrease battery performance. If you’re making a lot of phone calls, you may want to turn 4G/LTE off to extend battery life. This option is not available in all areas. On iPhone SE, iPhone 6, iPhone 6 Plus, and later, there are options for turning off 4G/LTE or for selecting Voice & Data (VoLTE) or Data Only.
Voice & Data (some carriers): Choose LTE to load data faster. (This also turns on VoLTE.) Choose slower speeds to increase battery life.
Turn Wi-Fi Assist on or off: If Wi-Fi connectivity is poor, Wi-Fi Assist uses cellular data to boost the signal.
Set whether cellular data is used for apps and services. Go to Settings > Cellular, then turn cellular data on or off for any app that can use cellular data. If a setting is off, iPhone uses only Wi-Fi for that service. The iTunes setting includes both iTunes Match and automatic downloads from the iTunes Store and the App Store.