I am after any suggestions as to how I can track down large increases in data usage on an iPhone 4S.

This is happening on my wife's phone.

She has tried asking 2 Degrees if they can provide any further information and after a false start where they said "we can't tell you due to the privacy act" followed by a further phone call which curiously ended with the same CSR a day later the real answer seems to be that they don't have any more info that could help explain the data spike.

So, is there some sort of log on the iphone or logging application or similar that can be used to identify where this extra data use is coming from.

She has the phone connected to wifi at work and home so most of the time is in wifi coverage.

Some of the usage data from 2 Degrees shows the problem, the first column is presumably the date and time that the usage record was generated and the second column is mb:
25/01/2013 0:29 16.86
28/01/2013 7:48 0.85
28/01/2013 23:40 1.16
29/01/2013 18:15 1.35
31/01/2013 14:56 0.01
31/01/2013 18:53 0.45

5/02/2013 18:43 0.04
5/02/2013 21:17 0.14
6/02/2013 14:04 1.53
9/02/2013 10:10 1.92
11/02/2013 8:01 32.79

15/02/2013 9:42 0.37
15/02/2013 18:09 0.13
16/02/2013 7:08 4.81
19/02/2013 10:51 0.12
21/02/2013 1:09 0.38
21/02/2013 8:34 18.99


edit: Sorry, paste from Excel looked OK but table formatting vanished when posted :(