The bad news is that, if you are a millennial, you cannot afford to regard leaving voicemail messages as obsolete. There are four generations actively participating in the workplace. This is unprecedented. It means that, while Baby Boomers are learning to text, millennials also must become adept at using voicemail.
Increase the odds of getting a call back by mentally composing your message before each call. And remember, people hate it when callers state their name and phone number too quickly in voice mail messages – no one wants to listen to a message ten times to comprehend simple information. Begin by saying your name and company (if applicable). Then assume the person you’re calling doesn't have your number, so say your phone number twice. If your name is at all unusual, spell it the first time you say your phone number. Talk slowly like you were writing it down yourself. The second time you say your phone number, you can say it at your normal rate of speech. A gracious phone message is no longer than 30 – 45 seconds. Be pleasant, but also get right to the point. Keep your voice mail message to two points maximum. If you need to share more information, then say you will send an e-mail message with the rest of the details. Leave a specific message. There’s nothing more frustrating than a voice mail that says, “Hi, it’s me. Call when you can!” Even if you’re just calling to say “Hi”, tell them that in your message. End on a high note! You don’t necessarily need to say “Goodbye” at the end of a voice mail, because you didn’t really talk to anyone. Instead, try something like, “Look forward to talking* with you!”

Many messaging apps now offer the ability to send voice messages to contacts without having to make a phone call in the first place. Using this method, you're bypassing a phone call and voicemail entirely, but it serves the same purpose.
Website: https://www.affiliatedunicom.com/nec-telephone-system-support/new-extension-setup-voicemail/