Help change filename extension

Hi guys,

I have a small problem with my Samsung. I want to change the extension of a file in My Files, but I can't figure out how to do it. I enabled show extensions in the settings menu, but I still can't change them. Is this completely disabled? Is there some app that can do this?

I downloaded some album art and I want to change the extension from .jpeg to .jpg because otherwise Music Player won't see it. I can solve the problem from my PC, but surely there's some way to do it on my phone?

Any help would be appreciated.