why is my One S using mobile data when I'm at home on wifi?

[dawniefriend]

I've had my One S for a couple of weeks and firstly, am loving it! And obviously am new to this forum too...

But clearly I'm getting through much more data than on my previous phone (Nokia N8). I am on about 120MB already, when I used to use only 50 or so in a month. Now I was expecting it to use more data as I have notifications/sync on for Facebook, Twitter, Gmail (but not much else).

Looks like I will still be safely inside my 500MB monthly plan, but conscious though of keeping an eye on data use, as being a control freak I like to know what's happening.

I downloaded Onavo last night and am surprised to see that of the 10MB used today, about 2.5MB of this was before I had left the house (ie between midnight and 7am) so should have been on wifi.
Facebook and 'Android OS & others' are the main culprits, which I guess is normal?

I am new to Android, so have been checking all the settings. I have the wifi set to stay connected when in sleep mode as was wondering if it was doing all its syncing over 3G overnight or something.

Any thoughts/ideas from experts on here...?

Thanks

[dawniefriend]

Ok, I now think it may be a problem with Onavo not knowing what time it is?
I have logged it on their support forum.