Expand your message with 'We're sorry we couldn't take your call this time.' The inclusion of 'this time' or 'on this occasion' suggests that the voicemail is the exception rather than the rule.
Pepperdine's unified messaging system, Unity, is provided for employees of the University. This message system allows employees to access voicemail messages through both the telephone and email. Students who wish to have a voicemail must complete a voicemail request form at OneStop.

19. Hi, you’ve reached [employee name]’s voicemail box. [Employee first name] no longer works for [company name]. Please call our main line at [phone number] and we’ll be happy to connect you with a current team member who can help.
Users often don’t invest enough time into their messages, resulting in incomplete, unprofessional, or otherwise under-whelming greetings. Sure, crafting a greeting doesn’t sound all that complicated; however, there are a number of pitfalls users can fall into—i.e. informality, terseness, sincerity, lack of direction, and more. While none of these sound too catastrophic, they are often interrelated. As such, they tend to worsen any problem. For example, humor can cause informality, worsen ambiguity, and weaken sincerity. That being said, users should strive to avoid ALL these pitfalls.