How to remove your Google Voice account
As you can read on the ‘removal page’ link, it is yet not possible to delete your account.
Direct removal link: http://www.google.com/support/voice/bin/answer.py?hl=en&answer=154895
Helpful Trick: Obfuscate your profile info.
Because most accounts and profiles at Google Voice cannot be removed, we suggest you login and change your account and profile information altogether.
Make sure you are logged in to your account on the site and click on the profile or options settings. Locate the fields with your personal info (email, name, address) and fill in generic, random information instead. If you can only select from several fields, change anything personally identifying. If possible, use a homepage/URL field or long text field (such as Description) and put this line in it: http://remove.org/removal-requested. This may encourage webmasters and admins to create an easier removal outlet.
Helpful Trick: Removing online data
If you can’t find any contact info and still wish to ask something, for example a question about what exactly is removed, about data retention, etc., you may contact the domain owners using this info.
Helpful Trick: Remove third-party logins
If you signed up for Google Voice using a third-party login such as Facebook or Twitter, you probably want to revoke all access from Google Voice. Click here to find out how.