As the odds of receiving a call back from your voicemail message are already low, you need to be very specific about what you say in your voicemail to give you the greatest chance of getting a call back. What you absolutely do NOT want to do is make yourself sound like a salesperson making a cold call. Instead, you want to sound like a very confident business colleague who deserves the respect of getting a call back.
The voicemail message can be anywhere between 10- 25 seconds. Keep it as short as you can because the prospects need to hear the vital details in it.

It’s a good practice for each of your team members to have their own personal business phone numbers. There are many reasons why they shouldn’t use their personal cell phone number for business, so you’ll want to give them their own phone number through your VoIP provider or phone system.
iPhone users have another option: You can send a voice message from Apple's Messages by tapping the microphone button inside the text box (this works only when you're messaging other iPhones). By default, these voice messages last for only two minutes before they are deleted, but you can change that. Either tap Keep under any sent voice message or go to Settings > Messages and tap Expire under Audio Messages. You can set the expiration date to Never, but this affects only your record of the conversation, not the recipient's.