I have a confession to make: I haven't recorded a new voicemail greeting in nearly a decade. Since then, I've (hopefully) become more articulate, poised, and self-assured. But hear my voicemail recording, and you'd think I was still new to the work world, a little unsure of myself — and probably not an authority.
We don't have a Help Desk voicemail. Our rationale is that if there's a call during work hours someone will pick up. That's our guarantee as our number is only for emergencies. If the call is after hours, then it must REALLY be an emergency (C-level or high level manager) so one of us will answer. Anything else goes to the help desk.

-Hello. All of our operators are busy right now, but if you’ll leave your name, telephone number, a brief message, and the time you called, we’ll get back to you as soon as possible. Thank you and have a pleasant day.
The bottom line is that a business’s situation is likely to change often and rapidly, each of which need a unique and applicable voicemail greeting to cover the circumstances and timeline. For example, callers shouldn’t reach a business-as-usual voicemail, and therefore expect a return call within the business day, if the subject they’re calling is out on vacation for two weeks. Such a lack of communication is a recipe to lose that caller’s trust and tarnish the brand’s reputation.