I do. Fortunately I have very rarely been in this situation. Most of the time simbly talking to the opponent or calling an official is good enough. But if my opponent is definitely, obviously, 100% certainly cheating, I will get my point back. I make very certain to emphasize that I am not cheating. I tell my opponent: "You hooked me. If you don't change the call I will call your next shot out no matter where you hit it." If they don't change the call I simply take the next point, even if they hit to the very center of the court. After this I say: "The score is fair now. If you don't cheat again, I won't take any more points." I think this is perfectly justified if there is no official around. The only other option would be to simply accept it and face a certain loss. But that would both reinforce the cheater's behavior and give you an unfair loss. I do not like doing this but IMO it is a necessary evil in some situations. What do you think?