If I block a number on a line, will that person know the number is blocked
The person who owns the blocked number will get a recording saying the call can't be completed when they try to call you. If what you mean is you're blocking a number on a line in your account and can the user of said line know if you've blocked a number - if that user can access the Verizon account, then I think they can see how the Call Filter settings are configured.
