What you'll need
Account Number
10 digits (the phone number)
Voicemail PIN
4 digits (from voicemail settings)
Account Info
Name and address
Step-by-step process
Step 1. Unlock The Number
Go to the Google Voice website -> Settings -> Account -> Unlock.
Follow the prompts to unlock the number.
Note that Google may charge you a small, one-time fee for doing so.
Step 2. Get Voicemail PIN
Settings -> Voicemail.
Enable Call to Listen if needed.
Retrieve or set a PIN.
Step 3. Get Account Info
See what name and adddress Google has on file for your account.
Make sure you provide this information to us EXACTLY as it appears in order to prevent rejections by Google.
Step 4. Take Screenshot
Because Google doesn't provide a billing statement for personal Google Voice accounts, take a screenshot of the Google Voice settings page with the phone number visible.
This will be what you upload as the billing statement.
Step 5. Submit Port In Request
Once you have gathered all of this information, submit your port in request and we'll get working on it.
Things to keep in mind
Be sure to keep your Google Voice account active until the entire porting process is complete.
For more information, see Google's help page here: https://support.google.com/voice/answer/1065667.