I've got a new showerhead to put on but am not having any luck getting the old one off. My pipe wrench is not working. Any suggestions?

I've got a new showerhead to put on but am not having any luck getting the old one off. My pipe wrench is not working. Any suggestions?
You may remove the shower head by unscrewing the shower arm from the drop earred ell in the wall and pull the entire assembly out to where you can work on it. Good luck, Tom