1. Swipe down from the top of the screen, then tap the Settings icon.
   
2. Under the Connections tab, tap Data usage.
   
3. To change the displayed billing cycle, tap the Data usage cycle drop-down.
   
4. Tap Change cycle.
   
5. Select the Desired date and tap SET.
   
6. To set a monthly data limit, tap Set mobile data limit.
   Note: When the mobile data limit is active and has been reached, the mobile data block will remain in effect until mobile data is manually re-enabled on the device, the limit threshold is changed to a higher value, or a new data usage cycle begins.  If you set data usage limits on your device, they do not communicate with AT&T systems.  You will still receive AT&T system generated notifications as you approach your data limits.
   
7. Drag the Warning marker up or down to set the level at which you will be warned about month data usage.
   
8. Drag the Limit marker up or down to set the monthly data limit.
   Note: The data warning and limit will save automatically.
   
9. You can scroll down to also view Data usage by app.
   Note: To restrict individual apps from using data while running in the background, tap the Desired app > restrict background data switch. To restrict all apps from using background data, form the 'Data usage' screen, tap More > Restrict background data.  Your myAT&T account is anohter way to manage your wireless usage.