How to I delete a song from ITunes and re-download
You should be able to right click on the song in iTunes and "Delete" - it will then ask you if you want to delete the song from your computer as well, which you will allow. Then sync your device, which will remove the song that is on it (or just open up the music on your device and delete that individual song) - redownload the song, and put it back on your iPhone.