I have cellular data turned off for iTunes Match downloads. If I open up the music app, and try to download a song it will not let me. It is grayed out. However, I was downloading a playlist right after I finished setting up my phone. I had to unexpectedly leave the house. I assumed that once I left WiFi, the downloads would pause and wait for WiFi. This is not the case. I go to look and notice that 600MB of my data was used by the music app. I am pretty sure iOS 6 behaved in this way but now in iOS 7, it seems to continue your download on cellular data.