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.
Thank you for calling ABC Company. We are currently closed for the holiday. Our normal business hours are 8 am to 8 pm, eastern time, Monday through Friday. Your call is very important to us. Please leave your name, phone number, and a brief message regarding your call. We will return your call on our next business day. Thank you.

With OpenPhone you can record your own voicemail greetings directly in the app, upload your own voice clips or simply type your voicemail script.
It is appropriate to apologize for missing the call (especially during working hours) and reassure the caller that they will receive a return phone call as soon as possible.