You can try the reverse look-ups that are online, but other than that, you don't have a lot of options. I recently had a similar problem, and it was kinda maddening. I even tried calling the telephone company to try to log a complaint, but they had no way to id the other line, or to stop the calls.. . One option, if you want the calls to go away, is to put your number on the national do not call registry.