How do I go about handling theft of service or theft by deception?

I met with someone who presented some credit repair programs to me which included a 30 day repair service. Prior to receiving my money, he communicated with me regularly. Once I paid him the $600, not only did communication cease, I have been inundated with collection calls, even on my job; I'm receiving letters stating I filed Identity theft, and my credit scores never changed. I want my money back but I'm not sure how to start the process for the least amount of money.