The are called Callhanders in Unity
http://www.cisco.com/en/US/docs/voice_ip_comm/unity/5x/administration/guide/dom/5xcusag040d.html
Id recommend creating a call flow diagram to understand the requirements and how to build it.
For example, outside caller dials 555-1212, this rings phone x4000 4 times, then rolls to Unity.
Unity picks up x4000 and plays call handler xyz.
option 1 marketing (transfer to steve)
option 2 sales (transfer to Call Handler Sales)
Sales Call Handler
Option 1
Option 2
etc
