itunes match

When you play a song using iTunes Match it is downloaded to your phone in the background. In order to prevent your music from accumulating and taking up space on your device you have to periodically delete the music to reclaim the space. You can delete it all at once by going to Settings>General>Usage>Music, swiping across All Music and tapping Delete. Or, you can delete individual albums and artists by navigating to them in the Music app, swiping across the artist or album name and tapping Delete.