Often, people seeking privacy will request that their phone number be unlisted or unpublished. The terms "unpublished" phone number and "unlisted" phone number are sometimes used interchangeably, although they are not the same thing.
An unpublished phone number is a number that does not appear in a published directory of phone numbers, such as the white pages. An unlisted phone number is a number that is not listed under a directory assistance service, such as 411.
While unlisted numbers are not publicly available, unpublished numbers are still available to those who call their local phone company.
Phone numbers that are unlisted or unpublished can still be sold by your telephone company to other companies. However, numbers that are unlisted will not appear in any of the company's internal directories.
While unlisted numbers are generally unavailable to the public, some services, such as private investigators, charge fees to find unlisted numbers, often by using older directories that include the number before it was unlisted.
If you wish to have your phone number remain private, ask your phone company to delist it from all directories and ask them what other privacy-enhancing measures they suggest.