A word of caution to anyone who signs up for Google's Project Fi using a Google Voice number:
"You may lose your Project Fi number (it may be reassigned to another person)"
That's what just happened to me. I had my Google Voice number for years and now I'm locked out of accounts that were using it for 2-factor auth (including bitcoin wallets) because I didn't update them thinking I would be able to keep using my Google Voice number after canceling Fi. Nope.
When I signed up for Fi you neglected to tell me that I would lose my Google Voice number if I canceled. Now that my Fi account is canceled I'm locked out of certain services because I expected to keep that number for 2-factor auth. Unacceptable.— davy wybiral (@davywtf) December 22, 2017