asterisk users - Feb 2012 - Calling from extension that I don't create

Dear Moderator,

I need an assistance for below problem:
1. there are time incoming call from extension 100 that I don't create, how
to know where is the origin of this extension?
2. when I pick up the call, there is no sound at all, this is very iritating
me due sometime the call is made during midnight until dawn, how to handle
this?

Thank you for your help and assistance.

Best regards,
Eko Kukuh Wibowo
+62818325598

http://www.spidermetrix.com/sm120.php?refspider=flickvideo