change the skin on the arms
Are you asking for Anet to change the AP giving shoulder skins from the hellfire to the radiant?
If yes, you can try creating a ticket to see if they can, but they may not do it (whether it’s a “no, you made the choice” to a "no, it’s not possible) so don’t go in expecting the answer to be a yes.
It also could depend on when you made this choice. Remember, if you did this months ago, they most likely won’t go back and ask you nicely to continue earning AP for the other skin. Good luck.
I’m a Moose, a ginger moose even.