asterisk users - Jan 2005 - dial-back, call-back, what, is it called?

I want to set up a feature or extension where you can enter your number and
have asterisk call you back.  useful for overseas and some cell phone
packages.  I started with privacy manager but when I issue hangup() it seems
the context also terminates.  I'm guessing AGI may need to get involved and
include .call files or. . .

Certainly this has been done before but I don't know what to call the
feature to search for it.  I tried callback and ringback.  

If anyone has a brand name for it or pointers to a script that does this I
would be very grateful.  Thanks.

Here is what I had:

;Call back Extension
exten => 558,1,NoOp
exten => 558,2,PrivacyManager
exten => 558,3,Answer
exten => 558,4,Wait(2)
exten => 558,5,Playback(hello)
exten => 558,6,hangup
exten => 558,7,Dial(Zap/1|1${calleridnum})
exten => 558,8,DISA(no-password|local)
exten => 558,9,Hangup
exten => 558,103,Hangup

-Nate