I suspect Verizon sells their 411 list to foreign telemarketers or shady companies. These lists are called “leads.” People pay good money for contact lists such as what Verizon sells to these companies. Tell them you want unlisted, otherwise you will be bombarded with very little way of stopping the calls.
After Verizon goofed and didn’t make my number unlisted I was wondering why these telemarketers had suddenly got hold of not only my number, but the name associated with the account. I did not give out the number to anyone! These calls came in within the hour after I got connected. Four or five a day. After I changed to unlisted and changed the number, ensuring old calls would not be forwarded, the calls stopped entirely.