Ask HN: How is that legal for companies to send spam/ads letters?

Any time I move, create a new business or change company address, I start getting a tone of spam and advertising to my physical address. They know my name, company name, and address etc. Companies like Spectrum act like nothing happened when I complain to them, they just send me a link to some form to unsubscribe. Well, I never subscribed in the first place. How is that legal? How to stop it? It is getting out of hands just like those robocalls.