You don't do it each time, you keep a single prepaid SIM as your "spam number", like people have spam gmail accounts for online competitions and random crap. I

You don't do it each time, you keep a single prepaid SIM as your "spam number", like people have spam gmail accounts for online competitions and random crap. I've been doing this for years. I have a $2 prepaid sim in an old phone sitting in my desk drawer. It's always off, and I only turn it on to approve a new signup or something. That way they can sell my number to marketers as much as they want, it doesn't bother my "real" number with robocalls and spam texts. What's mostly surprising is the insane increase in spam texts in the last year or so of using this method. I used to turn it on once a month or so to sign up to a new site, and have a few random texts... these days I get dozens a month, only proving more than ever that this method is worth doing.