How to delete songs off of my Iphone 4?

I used to be able to delete them from Itunes but not anymore. You can slide your finger across the song on the iphone screen and it will say "Delete" in red but it actually does NOT delete the song from your device. I also have a lot of trouble ADDING songs. They won't be listed after i add them on to the iphone a lot of the time.

If you have iTunes on a computer you can easily fix this, all you need to do is open itunes and right next to the song, album, or artist there should be a checked box. Uncheck the box to make sure it doesn't get synced or check it to keep it or add the song when syncing. So then you don't have to keep deleting the song everytime you sync. You can also go on your phone and go to Settings>General>Usage>Music and you can then delete music. Unfortunately you can only delete all of your songs so hopefully apple will change that. So in the meantime just use the iTunes method.