On your box, go to voice.google.com you should be familiar with the interface.
Sign in to your account first.
In the top left corner, hit the burger menu buttonand choose the Legacy Google Voice option.
Next, hit the Gear icon in the top right and select prefs.
Within that, go to the Phones tab.
There, youll see your current number displayed, and next to it, a button labelled Change/Port.
During the process, youll have to drop your Zip Code, as well as a few more fields.
Google will then generate a few new available numbers for you, based on what you entered.
you better pick the one you like best and then continue through the rest of the process.
