I did a google search on Sarbanes-Oxley voicemail to learn more and from what I have read, I can tell you that you need to talk to a real lawyer instead of asking the forum.
Here is an example of what I am referring to:
http://www.csoonline.com/counsel/session25/question2834.html
QUESTION:
Do you have to retain electronic records such as e-mail, voicemail and call detail records? If so, for how long?
ANSWER :
Record retention is a hot topic because of Sarbanes-Oxley, but there have always been laws and regulations regarding retention of e-mails and other communications. A recent study by Osterman Research indicated that fewer than 50 percent of companies kept critical e-mails. You should speak with your attorneys to understand how to apply the laws to your specific situation.
Answer Provided by: Fiona Williams