thats the phone connecting to the data network.
the user could be browsing ringtones, wallpaper, ect
mdram4x4 is correct. This is how the data sessions on your device are documented on the bill. May I ask what price plan do you have? Such billing documentation was used on our grandfathered plans that are no longer available. Please reply to this message if you have any additional questions or concerns.
How is this possible when the phone is turned off, or not in use?
If it's turned off it can't happen, but if it's on, the phone is so "smart" it will still update using data. Hence "smartphone".