The secret they use is that the company with the list NEVER sends anything, it simply sells the list to a campaign or PAC or whomever, and THAT group DOES remove you, but the moment a new campaign or PAC or whomever springs up, they buy the same list again.
This is why every campaign is a new legal entity each time around.
Indeed, My 90 year-old, deeply religious mother sent a televangelist $10 one time. A year later when she was in the hospital for a few weeks. I picked up her mail once a week and quickly found out I had to bring a large sack for one week of mail. For every actual bill she got, there were over a hundred pieces of physical spam mail from every kind of religious and political cause, candidate and prophet imaginable - usually in large four-color, glossy envelopes.
It's not just offshore call center con artists preying on the elderly. There's a huge, highly profitable, legal-but-scummy onshore industry too. It was obvious that 'nice Reverend on TV' sold her out to anyone who'd pay - and then they sold it and so on... Even though I'm an atheist, these assholes make me wish there was actually a hell full of fire and brimstone awaiting them.