Washing machine valve

https://imgur.com/a/WHpU0

Our hot water valve was leaking. We tried to replace it, but we can't get it off. We are holding the nut and the top won't spin off. We tried whacking it with a hammer, but it just won't budge. I realize that we can cut the plastic pipes and install a new system just a little lower on the wall, but is there any way we can get this valve apart and do the quick simple fix? I need to do some laundry and don't want to have to go to the laundry mat. Thanks.