Note: The primary phone number cannot be unassigned from the Auto Attendant. To release the main number, you need to swap it with another spare phone number on the account. Released numbers can be later assigned to a user, a Hunt Group, or any other object on the account. Toll-free numbers cannot be used as primary users' numbers.
That’s the simple structure of a voicemail greeting. Overall, your greeting should be professional, but the wording can vary depending on the situation. Check out a sample below.

The general voicemail greeting is used as the default voicemail greeting if you don't set any other greeting type. Occasionally, during events like power outages, even if you've set another greeting, your personalized programming might be wiped out. Or you might simply forget to change the greeting after returning from vacation.
A potential new customer gives your business a call. Nobody picks up the phone and the line just rings out. The customer doesn’t know why nobody answered and they don’t even know if they’ve called the right place. Perhaps they decide not to call back at all.