A straightforward search for the term brings up large sites in the UK, India, Malta and Hong Kong. "Directory Enquiries" was (is?) the name for the service in the UK where you pay a fee for someone to look in the telephone directory for you.
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That is probably fair. Anywhere I've lived in the US, someone would know (well, maybe not if they were young enough) what you meant by "telephone directory" but almost everyone would say "phonebook" at least in casual conversation. It's also true that when you would dial 411 for a number, that was called directory assistance. (And a listing of phone numbers for the staff in an organization would probably be called a staff directory or a telephone directory or something along those lines.)