“By endorsing this check you agree to not send me any future solicitations” and [then]sue them if they continue harassing you.”
Is that worth the cost of suing? The attorney will be charging you by the hour. Sounds petty. Reminds me of ... leftists at universities in the 1970s ... “teaching” anti-social, anti-corporate activism ... pay a bill by check for all but 5 cents or less, so the company had to spend a dollar to collect the other 5 cents. Eventually late fees and bad credit ratings wiped and turning things over to collections stopped some of that crap.
The amount of spam is obscene.