You can fine-tune this similarly to how companies A/B test their websites, ads, call scripts, and anything else that requires a change. The more elements of a call you look at, the more likely you’ll be able to optimize your voicemail greetings. If you jump right into the greeting without saying “Hello,” go back and make your greeting more personal on the second attempt.
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.

I have a confession to make: I haven't recorded a new voicemail greeting in nearly a decade. Since then, I've (hopefully) 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.
Your prospects need to hear something which can make them hold on to what you are trying to tell them and that starts with a good attractive statement.