How can I trace a telephone number that is VoIP back to an ip/provider?
Can I trace an 800 number and exchange back to a provider?

I know that the PBX is Asterisk. (default prompts and scripts)

Someone setup a PBX and recorded messages that sound just like my business'.
They don't have any valid entries. All options/extensions go to the same person.
An * will get me to a password prompt, but looks like any default passwords have been changed.

This was setup for fraud.