When I receive a text message to my Google voice number, I get a notification from my text application, as well as the Google Voice application. It would seem that the message is being forwarded to my cell number, but I've turned off text forwarding in the Voicemail & Text settings. Is there another setting that I am missing?
From Google Voice settings (on the web, not the phone app), under phones, select your mobile number, and Edit. Uncheck "Receive SMS on this phone"
Make sure you have updated to the latest version of the Google Voice application in the Market. Then open the app on your phone.
Go to: Settings > Sync and notifications. Uncheck the "Notifications via text message" box. Back all the way out, and just for good measure, reboot your phone.