Voicemails need to maintain a professional consistency that’s aligned with the entity it’s representing. That said, the structure can vary depending on the situation. There’s no template set in stone. In fact, trite and generic should be off the table. The goal should be a balance of uniqueness and practicality.
By default beginning April 2017, voicemail transcription is available for all Phone System in Microsoft 365 users. When you receive a voicemail, the message will be transcribed in the body of the voicemail email you receive in your mailbox. If you do not want to have transcription for your messages, ask your admin to disable it for you.

“Hi, you’ve called [name] at [XYZ company]. I’m currently busy [hiking through a rainforest, exploring China, climbing Mount Peru etc.] and so I can’t take your call right now. I won’t be back in the office until [date] and I look forward to hearing from you then.
It’s a good practice for each of your team members to have their own personal business phone numbers. There are many reasons why they shouldn’t use their personal cell phone number for business, so you’ll want to give them their own phone number through your VoIP provider or phone system.