Nella Braddy Henney, The Book of Business Etiquette
“ He should first make sure that he is calling the right number. In New York City alone, forty-eight thousand wrong numbers are asked for every day by subscribers who have not consulted the telephone directory first, or who have unconsciously transposed the digits in a number. For example, a number such as 6454 can easily be changed to 6544. The telephone directory is a safe guide, much more so than an old letter or bill head or an uncertain memory. ”
