Last year I stupidly answered an ad for St. Matthew's Church and sent them $5. I then realized my mistake, but after a dozen written requests to be removed from their mailing list got no response except more letters, I tried another route.
I wrote a very respectful, but firm letter saying that if they did not remove me from their mailing list, I was going to sue them in Small Claims Court in Tulsa for harassment, annoyance, mental cruelty, etc. And I indicated that I had sent a copy of this letter to my lawyer.
To my amazement, the letters stopped!
Then I heard from someone that they too had been unable to get off the mailing list and had taken some revenge. They made a several hundred photocopies the return postage-paid envelope, cut & pasted them together and mailed these fakes from several surrounding towns. They even sent several dozen to friends in other cities! Wow, what a great idea!! If everyone did that, even just 5-10.....hm...yes, they said it took a few hours of cutting and pasting, but what sweet revenge!