Some sales organisations never leave any voicemail. This is a mistake. If people have their voicemail enabled then they expect you to leave a message. You should leave at least one message. Otherwise, your number will likely be marked as SPAM and your reputation suffers. Leaving voicemails can be a tedious and time consuming business if you have to do it on 30-50% of calls you make. An hour of your day could be just talking to an answering machine! Then you have to remember,

Monitoring KPIs is essential to help your staff perform at their best ability while ensuring a company's long term success

Improving your call completion rate can significantly boost productivity, pipeline efficiency, and overall conversions.