> If you don't want your phone number leaked don't hand it over to a random website that pinky swears it won't keep it.
What's the worst they can do with it? Call me all hours of the day trying to sell me an extended factory warranty for my free Medicare brace that, by the way, has a Security Number that is under arrest by the Security Administration because it made fraudulent IRS payments with iTunes gift cards to lower my student loan payments because I didn't listen when Microsoft called about my Windows Virus?
Oh, wait, sorry, it hung up on me after dialing because their call center was full. Even if they answer, they just won't play anymore - as soon as they think you might be messing with them (or just aren't going to buy whatever they're selling), they hang up. Twenty years ago, you could have an hour long conversation with the credit card people if you were bored...
Even with spam blockers in place, that sort of garbage is the bulk of the calls my phones get. At least for my personal phone, I live in a different area code from where the phone is (insert XKCD about your area code being where you lived in 2002), so anything that's my phone's area code and not in my contact list is clearly unwelcome.
Phone numbers just aren't a large space to randomly dial looking for valid numbers if you're on a scum VOIP gateway, and clearly the scammers and spammers already have lists of what might be worth calling.