Received a call at my area code 408 business number in Sunnyvale, CA.  Wasn't able to pick up at the time.

Tried to call back the 306-304-9434 number later and heard a message "This phone number has been diconected".

This appears to be a spoofed number, or they are playing a fake "disconnected" message.  In either case, this would indicate illegitmate activity.

Any suggestions on how these people can be identified and stopped?