The role of the auto attendant is to route calls (according to a set of rules that you define) to the correct Hunt Group, and ultimately a single User Extension, where a team member should answer the phone. Only if that person is not available will voicemail pick up. The auto attendant itself has no ability to take a message, it’s the voice mailbox function that is triggered when the auto attendant fails to connect to a specific user.
For example, callers dialing one number may be routed differently than those dialing into your company via another direct inward dial line. In addition, callers selecting certain extensions may have different experiences depending on the rules associated with that specific auto attendant.