Cellular Data settings for individual apps won't work

On my iPhone 4, I'd like to leave the cellular data on for system functions such as Find My iPhone, etc. But I don't want most apps to be able to use cellular data. I know where the settings are (see this Apple support page Learn about cellular data settings and usage on your iPhone and iPad (Cellular Model) - Apple Support -- bottom of the page), BUT, it doesn't work. I can turn it off for various apps, but it turns it right back on. Have attempted restarting phone, etc. Nothing seems to help.

Anyone know how to solve this?? I found one reference to someone else having the same problem here: Re: Controlling the Cellular Data?