If you started your company more than a year ago, it’s probably time to change your voicemail script. Your recording should match the brand, tone, and voice of your company — just as though a caller were speaking to a member of your team.
Your phone system can be a powerful marketing tool for your business, and that includes your voicemail greeting. If you want to utilize this opportunity to throw in a quick humblebrag and keep callers informed of your awards and accolades, there are a few best practices, you should follow. First, keep the self-promotion brief and appropriately placed within your voicemail message. Don’t promote yourself and your products/services in the same greeting, and finally, only include current achievements in your business voicemail greeting.

This topic describes how you can manage an extension user's personal greeting, including playing, downloading, and deleting greetings.
The basic rule of thumb is that callers should hear one of two things when they first connect with your voicemail — either an apology for not being able to answer the call or a “thank you” for having called. You can do both if you prefer, but keep it short and to the point.