Instead of managing multiple voice mailboxes from multiple phones, forward your phones to one voice mail system. For example, I forward my mobile iPhone on AT&T to my direct work phone number for unanswered, busy or phone off. If I do not answer this transfers the call to voice mail. Then I have one voice mail system to learn and manage. Plus, in my case, I take advantage of the Cisco voice mail features such as unified messaging, inbox rules, notifications and alternate greetings. The link is a tutorial on call forwarding for the iPhone on AT&T. It is a similar process for other mobile phones and service providers. Remember first to setup your voice mail (i.e. greeting) and test it.