Free spam call blocker

I downloaded a free guide from their website on writing a children’s book. Now they keep calling me non-stop, they phone me more than my own mother. From about two days in they started calling three times a day. I kept telling them I’m not interested I didn’t have time to write a book yet for them to publish. A year later they still call, and they have all different numbers. Blocking stops the call ringing but still gives them voicemail access. They apparently take money and don’t publish books.