How to delete photos off of iphone 4 s?

I've deleted all my photos off of my phone but i my usage it still says i'm using way over 5 gb of memory i go to delete that usage but its still there how do i remove it permanently

If you don't have necessary files then format it. Or the problem might be of virus. Try using updated anti-virus to scan and remove the files.

Try PhoneClean (a desktop app) for Windows/Mac.