When synchronising ringtones from iTunes to the iPhone, you may accidentally have duplicate ringtones stored on your device. This is a common occurrence if the ringtone was purchased in iTunes on your computer as well as from the iTunes Store application on the iPhone. To remove the duplicate ringtone from your mobile device it must be manually deleted from the iTunes library, which will automatically remove the duplicate from the iPhoe during the next synchronisation between the program and the iPhone.
Run the iTunes program on your computer. Insert the USB cable for the iPhone into the iPhone's docking port, and insert the alternate end into your computer's USB port.
Click "File" at the top of the iTunes' program window, and click "Find Exact Duplicates" on the pull-down menu. Locate the duplicate ringtone in the iTunes duplicates list, and right-click the duplicate ringtone. If using a Macintosh computer, hold the "Control" key and click the duplicate.
Click "Delete" on the pop-up menu, and click "Delete" in the pop-up window to confirm you wish to remove the ringtone from your iTunes library.
Click "File" on the iTunes' program window, and click "Sync" from the pull-down menu to synchronise the information from iTunes to the iPhone. Alternately, click the "iPhone" tab under the "Devices" section of the iTunes' sidebar, click the "Ringtones" tab in the main window, and click "Selected ringtones."
Uncheck the box next to the duplicate ringtone, and click the "Apply" button to apply the new settings.
Click the "Eject" button next to the "iPhone" tab in the iTunes' sidebar, or click "Controls" at the top of the iTunes' window and click "Eject iPhone" on the pull-down menu.