"[Auto-attendants] assist a business of any size in presenting a more organized, efficient, and, if necessary, more robust picture of itself,” points out Brandi Armstrong, Co-Founder of Telecentrex and blogger on evancarmichael.com. The right greeting can make the difference between a frustrated customer or a satisfied one.
Sound upbeat in your message. When recording, be sure to say your message with a smile on your face. It’s obvious when people aren’t happy in their message. Since your work revolves around keeping happy customers, do your part by keeping a happy-sounding voicemail message.

While a short recording may not seem like a place to win new business, the professionalism, courtesy, and clearness that you convey in your greeting will leave a favorable impression in a customer's mind. For more tips and scripts on professional phone and voicemail greetings, here are some additional blogs:
Solution: Poor sound quality is unlikely the fault of a reliable business voicemail service that uses VoIP technology, Baldwin says. So garbled voicemails are often due to callers’ poor mobile phone reception while leaving their message—and you may just need to call them back, assuming you can figure out their phone number. But if the problem does seem to be your voicemail, make sure you’re using a business phone and voicemail service that uses VoIP and not relying on, say, your mobile phone’s voice mailbox.