In a voicemail or email leave a compelling reason for someone to call you back.  Raise a question in their mind about information in your voicemail message or email that will propel them to reach out to you.

In your own voicemail greeting, don’t tell the person to only leave a message, give them a compelling reason they might want to do business with you. Do so in ten seconds or less.  They called, so why not take advantage of the opportunity.  Do the same with your email out of office responses.

How do you know you succeeded? They cut right to the chase and say, “Tell me about the thing you mentioned in your voicemail or email.”

“We progress though change.” 
-John Paters