Just an FYI, i dont think you can actually call the restaurant directly. Im guessing the previous poster meant "disney dining" and not the actual restaurant.
@DisneyStarWisher I believe if you cancel LESS than 24 hours, you will be charged the $10pp fee. But perhaps if you call disney dining and are trying to replace the ADR with a different restaurant the same day, they wouldnt charge you the fee. But overall cancelling the same day, yes i think you'd be charged.
Perhaps someone else can chime in with more info....