The cellular connections made by your iPhone can have an affect on your device’s battery life. 3G and 4G signals may be quicker, but they also have a significant impact on your battery, especially if you’re in an area with poor signal.
To turn it off, open Settings, select Cellular (or Mobile Data in some regions) and turn off the Cellular Data / Mobile Data option. You can also do this to restrict all data use to Wi-Fi if you’re currently connected to a wireless network.
If poor signal is affecting your battery life you can also enable Airplane Mode from Control Center or the Settings app. Remember to turn it off again if you want to receive communication from others and notifications from apps.
Turning on Airplane Mode is also handy if you’re out of the country and want to avoid heavy network charges or save battery without having to turn off your device. Simply swipe up from the bottom of the screen and tap the Airplane icon. To reactivate connections, tap the icon again.