[aiharkness]

You enable and disable mobile network using manage connections (or it may have a different but similar name on your BlackBerry). It's the same place you enable and disable wifi and bluetooth, probably.

In the mobile network settings screen in options you have a settings to disable data, disable data when roaming, and so forth. On this screen, if you disable data, you turn off data on both mobile network and wifi.

You need to decide what you need to do. The above and what I posted earlier should be the information you need to decide your best approach, or at least help. I don't know anything about O2 or the app you are speaking of.
Posted via BlackBerryForums.com Mobile