Is there any way I could disable the system services that use data when I am not connected to wifi?
Well, as long as your iDevice is not jailbroken, sadly there is no way to fully do that, but you can disable some of them here:
Settings > Privacy > Location Services > scroll all the way down to the bottom > System Services
(At least with the iOS versions up to 7)
Just take out the SIM card and put it back in. That resolved the problem for me.
You can't select which system services have access to 3G from that page. Many system services' data use can't be switched off—only the services themselves.
Settings>iCloud>iCloudDrive>Use mobile data. Turn it off. All other cellular datas you need to turn off are already mentioned in the other answers.
I agree with user185442. This seems to be impossible. I spent a long time disabling data traffic for all non vital apps and services, including things like Music, iBooks, App Store and a large number of 3rd party apps. I still got 912 MB "System Services" usage in an afternoon. The culprit (apart from Apple's programmers) seems to be iTunes purchases, that probably somehow were downloaded over 3G, even though Mobile Data was disabled for iTunes & App Stores.
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