can a caller transfer themselves to another extension

i believe ext-to-ext dialing will work, and it is active by default - you don’t need to configure anything.
The only thing you need to do is to edit your voicemail to something like this:

“Please leave a voicemail after the tone, but if it’s very urgent - please dial extension 789” 

Of course you can use any extension number.. 789 was just an example.
 

That’s it! Thank you, yes. Dial the alternate extension, then # and it will transfer you to someone else. My assistant in this case!