Rehearse your greeting a few times before you press record. Plan your pauses and select natural places to take a breath. If you are recording directly into your phone don't hold it to your ear like you are talking on the phone. This can produce a muffled tone. Hold the phone out in front of you a few inches from your mouth for the clearest recording. This may require some trial and error. So playback your greeting and make necessary adjustments on your re-record.
Hello, you have reached X (service provider). Unfortunately, all our agents are engaged in talking to other customers. You can stay online or to resolve something urgent, try our live chat service. You also have the option of leaving your name, ID and number and our agents will revert to you at the earliest.

If you’re planning on doing a sales call sprint via phone – so, possibly via voicemail – trust the scripts crafted by close.io’s Steli Efti on this one . Finally, since it tends to come out of people nearly automatically whenever they leave VMs on phones: Please don’t say “I tried calling you” or “I wasn’t able to reach you.”
Friends and colleagues speak to each using first names only. So do people of authority. They do not call each other and leave voicemail messages asking for Mister, Miss, or Mrs. Therefore, when you call a person you want to do business with and you leave a voicemail message, refer to them by their first name only. Don't say mister, miss, or misses. Don't say their last name. Begin your voicemail message by saying only "hi/hello" followed by the person's first name. Or, you can even forget the "hi/hello" and just say the person's first name. That is how you show confidence and authority and separate yourself from weak salespeople.