Internet/Fraud Case - PLEASE help =(

Someone answered a Craigs List posting that was soliciting sex and posed as me, giving out my name and telephone number. This person obviously knows me since not only did they have my number but were able to give a full physical description of myself in their emails. The gentleman they responded to has been very kind in forwarding me emails that were sent back and forth between the two last week detailing what would happen when they got together. I contacted yahoo (since the person posing as me was on a yahoo mailing address) and they were not much help. Do I have a case here going to local authorities (I'm from NJ if that matters..)? What steps do I take?? Please help!