There may be either an update that the phone is trying to get (for the phone itself), an update for an app on the phone, or an app is bad and trying to update/add things to the phone that it shouldn't.
You should check the phone and find out what is trying to update/download exactly. That will give you a better idea of what is going on.
You can also set up your phone to not do auto updating, but then you will have to remember to manually update.