While serving as family IT support I was dealing with a Sierra mobile internet dongle on a new Win 8 lappie. The complaint was that it was draining all its prepay credit wayyyyyy faster than the previous XP lappie. The ideal solution seems to be to define the mobile connection as a metered connection to stop Windows downloading all sorts of updates & crap in the background. Unfortunately its doesn't seem to be able to do that. The newer Vodafone vodem appears as a broadband connection, and defines itself as a metered connection, but the Sierra one doesn't appear in in the list, it seems to just work through the Sierra 3G Watcher app.
Any ideas?