It's happened a few times - years ago, I would go with the flow and enjoy it (if I wanted it to continue). Other times, I politely say I have a hands only rule and that usually turns into a different fun time. Never had anyone get offended. I do the same if I'm not looking for oral and the masseur wants to do it or positions their cock in my face. Again, no one has ever had an issue. There's always a way to have safe fun