Do you have a file manager, such as Astro? It's free in the market. You will need to go into your directory to see if indeed the photos are on your phone twice and delete one.
A second alternative is to backup the photos and videos to your computer, then delete them from your phone. Once you see that they are not there, anymore, put them back where you want it.
Further than that, your carrier may be able to provide tech support if you're not getting the answers you need elsewhere. Hope it helps!