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.
Follow the instructions and press that number. You will be asked to delete your current Voicemail greeting. Click on the ‘Yes’ button that appears on the screen if you want to remove that. You can save your new recorded Voicemail greeting or can use the default recorded option. From the home screen, select the Phone app. Note: Alternately, you can set up voicemail by selecting the Phone app then selecting and holding the 1 key. Select Keypad, then select the Visual Voicemail icon. Select Start. Select Ok. From any Home screen, tap the Menu key. Tap Settings. Tap Call settings. Tap Voicemail. Tap Voicemail again. View the voicemail number. Press and hold the 1 on your device’s dial pad to call and connect to your voicemail. Press the star * key to access the main menu. Press 4 to access the mailbox options. Press 7 to change the language of the voicemail prompts to either Spanish or English.

This is something that can be done, yes. But I can't think of a time when a salesperson would want to do it. Best-case scenario, the timestamp will alert the prospect you left a voicemail at a late hour or on the weekend, and they'll wonder why. Worst-case scenario, they'll just think your desperate.
After each one, evaluate your performance. Most systems provide the option of listening to the message you just left. Doing this as much as possible will improve your performance more than anything else. Would you save that voicemail? Would you return that call? Would you return that call right away? Are you missing the basics (alternative phone number, optimal ways to get in touch, a fall-back person to call)? Did you craft it or wing it?