6.7. Agent Callback 
Agent callback enables a caller in the queue to leave a voicemail (callback request) for agents. The voicemail retains the position of the original caller in the queue. As soon as an appropriate agent becomes free, that agent receives a call, hears the voicemail left by the caller, and can then call back that caller.
INFO:
Voicemail numbers are not allowed as callback numbers. In cases as such, the call
returns to
the initial prompt menu, where a new number should
be provided (#2).
If the agent reaches the caller, he or she can flag the callback as completed. If
the caller cannot be reached, the agent can schedule a timed reminder for the callback
to be repeated. At the time of execution, it is placed back in the associated queue.
In order for an agent to receive callbacks, this feature must be enabled in his or
her agent assignment.
If a preferred agent has been set for a caller, an attempt is first made to route
the callback
requests of that caller to the preferred agent. If
the preferred agent is not available, the callback
request is forwarded to any available agent.