I noticed the Spotify APP does not remove music content from the phone's hard drive when a playlist is switched from offline to onlineplayback. 

I first noticed this issue when removing songs from an offline playlist.  I noticed  that the size of the spotify app remained the same regardless of how many songs I removed from the offline playlist.  I then tried turning the playlist on and off (annoying, because it would require resyncing) to fix the problem. This made the situation worse. I lost the availability to play the playlist offline and the app still occupies the same amount of hard drive space. The only other solution I can think of is to uninstall the entire APP?  I hope this is not necessary.