SoftBank Mobile announced that it's shutting down all 2G mobile services, which have been in operation since April 1994, on March 31, 2010. The company will focus all resources on its 3G services that began in December, 2002. Existing 2G users will receive notices on what they need to do to upgrade.
http://www.softbankmobile.co.jp/ja/news/press/2008/20080703_01/index.html (Japanese)