I've tried restricting background data, uninstalling apps etc, etc.....then the phone is virtually useless.
Hi Lucinda. It's possible that there is still an app that you haven't restricted internet access or uninstalled. As a last resort you can edit the APN and add or remove a single letter from it. That will surely restrict data. When the time comes that you need to use data, just edit the APN again to the correct value. Hope this helps you.