When people started calling my personal mobile number with questions about a voluntary organisation I'm involved with, I was confused: we weren't sharing that number. It turns out that Google had decided to take the number I used to verify my identity for Google Business some years prior and start putting it in Google Search results. WTF, Google?
The phone company definitely did charge extra for unlisted numbers. The number lookup service, which was just called “Information”, was accessed by dialing 411 - the origin of “What’s the 411?” In the olden days you got a human being, then they automated it with voice recognition. In most places 411 doesn’t exist anymore but it was in service until only a few years ago.
Wait, I suspect that we don’t live in the same country.
In Italy keeping the number unlisted was free (you just needed to declare it when you were signing the contract) and I have no memory of something like the 411.