well, you can log the calls and record any audio that you can. Then turn it over to the local police and also submit a copy to the FBI or US Secret Service. After that, change your phone number and go on with life. ALso, file a written complaint with your phone carrier and copy that to the relevant authorities. Now, I haven't been a target myself, but I know several people that have. They took the above actions and started having some peace and quiet in their lives afterward.