My old work number was 1 digit off of the local Department of Defense office and I would get calls for them all the time asking about benefits, the location of checks and whatnot.

It was bad when the caller didn't believe that I WASN'T the DoD. Several thought I was just giving them the run around.

The worst though, came when the DoD sent out letters giving people MY number as the one to call. I called the DoD, explained, they promised to send out corrections.

I had my phone number at work changed when they sent out the second letter still with my old number on it.