> Why would moving require a new provider/number? Are plans/numbers not portable in Europe?

They are portable in Europe (I said that in the second part of my comment), but it seemed like they weren’t in the US, because otherwise, the post is a bit strange. The author just tried every number from his area code to find the owner, when it is possible/likely that the owner has a completely different area code. That’s why I thought it might be that the current number always reflects the actual area code.