Google US Accept Mobile Number Porting to Google Voice Service
If you are using the Google Voice service in US, you can now port your mobile number to the Google Voice to be your primary number. With a one time $20 porting cost, the process will take about 24 hours to complete. Note that the porting process also means that you will terminate the existing contract with your service provider. You will then need to subscribe to another mobile service with one of the carrier, and and configure your Google Voice account forwarding setting to that new number.