I usually only enable the data connection on my phone when I'm actively checking my mails and messages as I have a tight data limit (which works fine for me). Recently I activated my 3G data connection while listening to local mp3 via Xbox Music, and noticed the app would eat into my data allowance. Is it possible to prevent Xbox Music from using online services, and if so, how?
The only feature I know that allows you to restrict your data usage in the Xbox Music app itself is to launch the app and choose the "Settings" menu from the bottom of the screen and then toggling off "Connect to streaming music" option.
I assume the app would still use small amounts of data when you launch it to pull the new music offered in the music store (this is visible by swiping left on the main screen of the app) and possibly album information. This should be very minimal though.