Hello taliaw15,
I definitely understand wanting to remove duplicate songs off of your iPhone. If you want to directly manage what is on the phone, you might want to enable syncing manually and delete the duplicates from the Music section of your iPhone in iTunes.
I found an article with steps on manually managing your music on your iPhone. I wasn't sure whether you were using a Mac or Windows computer, so I included both articles. You can find the steps to manually manage your music under the section titled "Sync your device manually" in the following articles:
iTunes 11 for Mac: Set up syncing for iPod, iPhone, or iPad
http://support.apple.com/kb/PH12113
iTunes 11 for Windows: Set up syncing for iPod, iPhone, or iPad
http://support.apple.com/kb/PH12313
If you have an earlier version of iTunes, you can use this article:
iTunes: Syncing media content to iPod
http://support.apple.com/kb/HT1351
Thank you for posting in the Apple Support Communities.
Best,
Sheila M.