To create a greater sense of authority, and that you are somebody important, list the name of a person and company who you've worked with before, especially if that person and company is a direct competitor of the person you are calling. Nothing grabs the interest of the person you are calling faster than hearing the name of their main competitor.
You can also go to Settings → Phone → and make sure you see Change Voicemail Password.

Hi, you have reached …. Please leave your name, phone number and a message and if we like it we will return your call.
In order to leave an effective professional voice mail, there are crucial techniques to master: The way you sound is the most important thing to remember. You want to leave a good and lasting impression on the person you called. People respond better to positive and energetic tones, keeping in mind to use an authoritative voice. People tend to respond and feel more comfortable if you have a mutual friend, contact or co-worker in common. Mention it! If possible, finding a creative link makes yourself memorable. No one wants to listen to a rambling voice mail especially in our fast-paced business culture. Sometimes upon retrieving voice mail messages, a recording tells you how long the upcoming message is. If it's too long, you will probably be deleted before you have even been heard. When you focus your message on one clear and confined topic, you will most likely get a call back. Open ended voice mails are unfavorable among clients. The point of a voice mail is to get what you need answered. Tell them what you want them to do, e.g. "Call me back." "Check out my website." Say your contact information clear and slow. Most of the time people are listening to their messages on-the-go, so try to eliminate the potential of having them repeat the message over. Leaving your email address as contact option is a good way to come across less threatening