Share with your caller when they can expect a callback. If you return calls within 24 hours, let them know. Give them an estimate of when they can expect your call.
5. “Hi, you’ve reached [company name]. We can’t take your call right now but we will call you back as soon as we’re available. Please leave your name, number and reason for your call. We know your time is precious, so to skip the back and forth, kindly leave a few different times of day that work best with your schedule and we will do our best to reach you then! Have a great day.” This greeting lets your caller know that not only your time is precious, but you realize theirs is as well.

If you have indicated you will be checking messages, ensure that you do so. If your ability to do so changes, remember to update your greeting. Tip: have someone else call your voicemail and check your greeting. You may not hear your own omissions.
Before the digital era, he says more than 80 percent of business lines had voice mail. Now, he estimates only a third of office phones have it.”For customers, even the most professional voicemail greeting is impersonal, and may even harm customer experience (millennials, in particular, avoid using voicemail altogether).