Users often don’t invest enough time into their messages, resulting in incomplete, unprofessional, or otherwise under-whelming greetings. Sure, crafting a greeting doesn’t sound all that complicated; however, there are a number of pitfalls users can fall into—i.e. informality, terseness, sincerity, lack of direction, and more. While none of these sound too catastrophic, they are often interrelated. As such, they tend to worsen any problem. For example, humor can cause informality, worsen ambiguity, and weaken sincerity. That being said, users should strive to avoid ALL these pitfalls.
https://www.indeed.com/career-advice/career-development/professional-voicemail-greeting

As an added bonus, posting a job on Voices.com is always free. They also have a VoiceMatch™ algorithm to match your job to only the most qualified voice talent.
Most mistakes are made right at the beginning. Many people do not know what they are going to say in advance and so they try to make a voice mail recording on-the-fly. Even only having a general idea of what you are going to say won’t really cut it. These types of greetings lack professionalism and sincerity. Write out your voice mail greeting word for word in advance and be sure to include information like: – The type of information that you need to return the call (name, number, details, etc)