Re: Voicemail for Auto Attendant & Call queueing. Yes, believe this was covered earlier, or in another thread. Basically need to have a user with UM/Voicemail enabled in your O365 tenant, then the AA routes to a "person". So it will costs you a full E3 license to enable UM/Voicemail.
While email and text support saw an increase in recent years, many customers, partners, and potential hires still prefer to call your company directly. When writing your voicemail script, include basic information such as a short greeting, your company name, an invitation to leave a short message, and the time frame in which the caller can expect a return call. If relevant, you may want to include your office hours, extensions for company departments, and the contact information for your office manager or HR department.

With all of these things to think about for a short 20-second voicemail, you might be feeling a little bit overwhelmed. We promise it’s actually is much simpler than it sounds.
Expanding on the simple approach above, let the caller know who they've reached. This will not only eliminate people leaving voicemails by mistake, but it will reassure the caller that they have called the number they intended.