Murray Leinster 
Sam, This Is You 

What if you could talk to the version of you who existed ten days ago, or the you who will exist ten days in the future? That’s exactly what enterprising telephone lineman Sam Yoder figures out how to do in the surprisingly funny science-fiction story "Sam, This Is You." At first, he focuses on the money-making potential of his little scheme — but before long, he runs into some unforeseen complications.