How to completely remove music from iphone?

I have an iPhone 5 with iOS 7, and I recently started paying for spotify. After a while, I noticed that my music took up a lot of my space. I have tried swiping and deleting, I have tried to turn off the "Show all music" and I have tried to resync the iPhone without any music, but there's still 1.8gb of music that won't go away. I need help!

Make sure on the sync page, on your desktop, that all the music check boxes are deselected. Also check to see if the option "fill free space with music" is on or not