Change your number
There is a one-time $10 fee to change your Google number. If you wish to change the Google number that you previously chose, you can do so through the Phones tab of your Google Voice Settings. Click the change link next to your current number to get started. You can choose an entirely new Google number or if you'd like to use Google Voice with your existing mobile number, you can port your number.
You will not be charged the $10 number change fee until you've confirmed the number change and entered information through the Google Wallet payment process.
Once you've completed the number change process, both your old and new Google numbers will appear in the Phones tab for three months after the number change. Calls to your old number will continue to forward to your Google Voice account for 90 days, giving you time to tell your contacts about your new number. At the end of the 90 day period we will email you with a list of contacts who are still using your original Google Voice number, so that you can update them.
Keeping your original Google Voice number
For a one time fee of $20, you can keep your original Google Voice number as a secondary number. All calls and text messages to both your primary and original numbers will still reach you. However, your primary Google number is the only one that will display on the caller ID when you make calls or send text messages. You can access this option by going to the Phones tab in your Voice Settings.