I managed to use up my entire mobile data (1.5GB) allowance in a few days this month, including getting a "you've used 80% of your data allowance" warning text a full 6 minutes before the "you've used 100% of your data allowance" (by my math, 400MB in 6 minutes). My phone has been playing up a bit of late (various apps crashing requiring a reboot), so I suspected it was indeed something screwy my phone was doing rather than Vodafone's systems deciding to send random texts.

I keep my phone pretty clean (no games or dodgy freeware), and haven't installed any obviously questionable apps. The phone's internal "data usage" page was pointing the finger at "Android OS" as the app that used the most data, and it's hard to uninstall the OS app, so was hoping (expecting really) that Vodafone would be able to tell me where all the data was being used in order to narrow down the likely culprits. 

Having spent a bit of time on the phone to Vodafone today and yesterday, I was very surprised to be informed that they cannot actually tell me where the data has gone, just that it was over http/https. Fundamentally I find this (a) pretty unhelpful in terms of diagnosing problems and (b) very surprising, given that if PC Plod produced a warrant to hand over data about my dodgy browsing habits I can't imagine "not having that information" is going to fly.

A Sydney journalist (presumably with a similar axe to grind) used Australia's equivalent of the Privacy Act to require disclosure of all data held about him/his phone by Telstra. This decision got overturned on appeal, but is being appealed again, so watch this space.

In the end, I gave up trying to diagnose the problem and factory reset the phone out of nervousness as to what was going on. Credit to Vodafone, they did give me 500MB free (although this may have been just to get me off the phone).

Having reread what I've just written, there isn't a question there, just have a grumble/vent.