You can have a Google Fi and a Google Voice number in the same account.
Transfer your Google Voice number to Google Fi
If you want to port your Google Voice number to your Google Fi service, select that option when you sign up for Google Fi.
Important: Remember to unlock your Google Voice number.
How long does the transfer take?
If you can’t transfer your Google Voice number
If you have problems transferring your number to Google Fi, contact a Google Fi expert. Keep in mind that some Google Voice numbers can’t be transferred to Google Fi.
Tip: When you switch from Google Voice to Google Fi, your previous voicemails remain in Google Voice. Voicemails you receive after the switch to Google Fi are found in the Google Fi app or by calling your voicemail.
Important: Some third-party services don’t accept phone numbers that originated from Google Voice. This includes after they’ve been ported to Google Fi. We recommend contacting any affected third-party service providers should this issue arise. You can get a new number with Google Fi and then set up your phone to make & receive calls from your Google Voice number.
To transfer your number from Google Fi to Google Voice, refer to these articles: