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You could probably contact Craigslist, but I doubt they would do anything for you.

Your only real choice would be to call the cops and have the subpeona Craigslist for the IP address and have them go to the service provider and find out who's doing it.

Unless you have a bored Police force in your town, I doubt they'll do anything but tell you to change your number. Craiglist might be able to ban that IP address though...
 
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