Should I leave voice messages

It is not worthwhile to leave voice messages.  It will slow you down when using the dialer.  

If you get a note that a professional needs to reschedule or maybe was a no show and you are calling back to get them on the calendar again, do not leave messages.  You will not get a return call.

Let's say you get a note that the professional needs to reschedule.  Do not call the professional and leave a message as you will almost never get a return call. These professionals will not return your call.  Therefore, the way to get them is to dial them each day (at different times) until they answer live.

You can also try calling from different numbers

see this article  https://setters.freshdesk.com/a/solutions/articles/153000111167

If you are organized and keep a good callback list, you will find that each day, calling your callback list will help you set an additional demonstration per day.

what to say when you all back? 

https://setters.freshdesk.com/a/solutions/articles/153000111255