Hello. You have reached [Name]. I apologize for not being able to answer your call at the moment. However, if you leave your name, number, and a short message, I’ll make sure to contact you when I return.
Rather than waiting for a callback, open up additional channels of communication with your callers by inviting them to email. The most professional voicemail greetings often include an alternative method of communication.

Even in today's fast-paced world, customers don't like being greeted with an automated message. According to the New York Times, callers of a certain age are put off entirely if they are answered by a voicemail instead of a real person.
I have a confession to make: I haven’t recorded a new voicemail greeting since 2014. In the past four years, I (hopefully) have 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. Obviously I need toupdate it. And if you haven’t changed your voicemail greeting in over a year, you’re likely in the same boat. After all, a professional voicemail recording boosts your credibility, makes you seem more competent, and encourages whoever’s listening to it to continue the relationship. A relatively unprofessional one — like mine, for instance — does the opposite: It encourages prospects, recruiters, and potential connections to run in the other direction. With that in mind, I’ve written 18 unique voicemail greetings for every situation. Pick your favorite, practice a few times, then record your new voicemail.