Telephone books are copyrightable. This is black letter law. As said by the Supreme Court in Feist, "Notwithstanding a valid copyright, a subsequent compiler remains free to use the facts contained in another's publication to aid in preparing a competing work, so long as the competing work does not feature the same selection and arrangement,"

In other words, if it does feature the same selection and arrangement, it is a violation of copyright.

Your statement that APIs are not copyrightable is not true as well.