In probably the best use of the directory in the last decade (outside of doorstops) The White Pages has an app feature that tells you exactly what business is trying to call you, even if it isn't saved in your contacts.
The feature, aptly called Who's Calling? has a caller identification feature that recognises unknown calls as they're received. By displaying the business name, the feature lets you know quickly if you want to pick up or not.
Since its rollout across Android devices in December last year and iOS in February, the Who's Calling? feature has successfully identified over 129,000 calls, according to White Pages. 32,800 business listings are updated daily, too.