Still need help monitoring

I need assistance monitoring a channel. All I want to be able to do is get the caller ID that is coming in. I can subscribe to events but I see all the channels. That would be fine but I don’t know how to translate the Channel ID to an extension number. What I get is something like:

SIP/0004F205E8EF-8605

What I want is something like:

802

How do I translate these? Any help would be much appreciated!