#1. Turn off mobile data usage for itunes and App Store downloads.

One very effective way to reduce iPhone cellular data usage is to “disuade” your iPhone from using your mobile data when you’re away from a Wi-Fi signal. As such, you won’t witness any automatic downloads that’ll sap your data without your permission.

Simply go to Settings > iTunes & App Store and turn off Use Mobile Data.

#2. Find out which apps are using the most data.

Much like I can find out which apps are using the most battery resources on my smartphone, so you can find out which internet-enabled apps are consuming the most data. Simply go to Settings> Mobile Data.

Here, you’ll find a series of buttons beside the apps that are consuming too much data. Toggle off/on according to your data preference.

#3. Disable some apps from refreshing in the background.

Another amazing way to reduce iPhone cellular data usage is to prevent some internet-enabled applications from auto-refreshing in the background without your consent thereby utilizing mobile data whenever they like.

Mind you however that certain apps, especially some instant messaging apps that need to load up new messages and friends’ activities in the background need to auto-refresh.

So, to disable the ones that don’t need this, simply go over to Settings > General > Background and toggle off/on to your specifications.

You can also read more on http://www.richeetech.com.ng/reduce-iphone-cellular-data-usage/