Why does iPhone continuously use 3G/data every hour, despite "everything" is turned off?

Every hour, one to several times an hour, the phone uses 0.1 to 20kb with 3G / GPRS. And this despite the fact that the following is off:

- WiFi

- Notifications

- Locations

- Push

Someone who can explain to me what/why the phone uses the GPRS for? I have unlimited GRPS included from my cellphone operator (NetCom in Norway), so this is no worries. However when I travel abroad, this can get expensive.

I know I just can turn of 3G, but I would still like to know why the continuos use of GRPS happens. In case it's an app or setting I haven't done anything with.

Just in case: no app is running :-)

Have looked online and there are many who have an opinion, but do not know. I'm looking for an answer, not what people think the the answer is :-)