Why tell ‘em anything? Just don’t do it. Make plans to do other things on the day they want your services the moment they ask you to do the job.
“No, on that day, I have made other plans already” Then give your money and time to groups who espouse your beliefs.
Their objective is to force you to do something you find unpleasant.... Forcing them to do something unpleasant helps them decide maybe they don’t want to spend their money with you.....