I am being cyber-bullied and stalked by a pedophile.

I have reason to believe I'm being cyber-stalked and bullied by a pedophile. Every few months I'll get a message from a New User on Snapvine, male, always insulting and saying crude things. I always delete the message, report, block and ignore the user but they keep returning. Now I have reason to believe I recognize the voice. It's a former friend I had years ago until they admitted to me they had interest in child sex, so I have severed all ties. Now I believe this person is back, hiding behind an anonymous call. Is there any way to track his IP or calling number and report him to the FCC or FBI?