Do you have iTunes Match? If so, this could be it. I'm not really sure. It's possible it has to do with syncing things over iCloud using cell data not wifi. Also try:May I know what does this 56.2mb of itunes accounts consists of?
This iTunes accounts keep sucking my data, the amount keep increasing.
Settings>Cellular> ...you may need to turn off cell data for:
iBooks
iTunes Store
Podcasts
Also check here:
Settings>Music>Show All Music-off ...Music app can display and play all music on all devices on your iCloud account (including iTunes on your computer), and play it, using cell data to do so. If you are in the Music app and see an iCloud cloud icon to the right of music tracks, those tracks are not actually on your iOS device, but on another device.
To use cell data for iTunes Radio, but not for automatic updates do this:
Settings>iTunes & App Store>Music-on, Apps-on, Books-on, Updates-on, Use Cellular Data-on
then:
Settings>Cellular> and turn OFF the following:
App Store
iBooks
iTunes Store
Podcasts
You need to have Music-ON here to use iTunes Radio over cell data, you can check the usage here, but, that is cell data for the Music app including:
iTunes Radio
iTunes Match (if using),
and streaming music from other devices on your iCloud account (see above).
Using these settings allows iTunes Radio to use cell data on the road, while waiting for wifi to do automatic updates. I found this out the hard way using the iOS 7 betas.
For those of you that use Pandora, you may find that iTunes Radio uses more data. You can track it here (Settings>Cellular Data), if you "Reset Statistics" (at bottom) on the same day of your monthly bill cycle.
Lastly, if you don't want to use iTunes Radio over cell data, only wifi, but do want to keep "Show All Music" on for use over wifi, do this: Settings>iTunes & App Store>Use Cellular Data-OFF (turn Show All Music ON) & Settings>Cellular>Music-OFF. This, (along with other settings above), will allow you to play music on other devices using your iCloud account (or iTunes Match), restricting it to wifi only.
NOTE: I have it set as I suggested for iTunes Radio over cell data, but auto updates wifi only, and I have over 16MB next to iTunes Accounts, so, I'm really not sure what it is about.