iPhone 5S

1. Touch Settings.

2. Touch Mobile Data.

3. Touch Mobile Data Options.

4. Touch Data Roaming to change the setting (e.g., from off to on).

5. Data roaming is now on.
Touch Data Roaming again to turn it off.

6. Touch Mobile to return to the previous screen.

7. To turn off data services completely, touch Mobile Data.

8. Data services are now off.
Touch Mobile Data again to turn on data services.