Extension Call Back


Can’t seem to find any documentation about this anywhere but not sure if my terminology is correct.

I have a customer that would like an extension call back facility.

Basically rather than keep calling in internal extension if they are busy they want to be able to set a call back so when the extension becomes free it calls them automatically.

They only want this to work with internal extension.

Seems like a normal request but not something I have come across before.

Anyone have any idea’s or know where to point me to get it working.