I try and keep an eye on my cell data so I don't use too much. From what I've noticed from my own usage the apps that eat up the most data are the ones that stream music and videos like Pandora and Youtube, so I turned off cell data for these apps. Just yesterday I got a notification from Pandora saying "New music has been added to so-and-so station". I wasn't on wifi and after double checking the cell settings data was still disabled for it.
Whats going on?