Project Fi invites started going out to interested users yesterday, and there are likely some people still seeing those invites come in. While most of the questions have been answered regarding how the whole of the service works, what you get, what you lose, where it can be used and what devices are compatible (only the Nexus 6), there seems to still be some confusion over the issue of what happens to Google Voice when you set up a Project Fi account. We have covered this on a couple of different occasions but it seems a new detail has come up which was previously unclear due to simply not being addressed. What happens to your Google Voice number should you decide to stop using Project Fi?
According to the Project Fi product manager Simon Arscott, users who set up Project Fi are able to bring their Google Voice number back to a Google Voice account if they end up discontinuing their Project Fi service. This should put some people's minds at ease in knowing that if they don't really care for Project Fi, they can stop their Fi accounts and reopen their Google Voice account with the same Google Voice number. As a quick recap, when you sign up for Project Fi, you'll be asked to choose a number, whether it be a completely new number (which can be ported over from another carrier service like T-Mobile or Verizon) or you can choose to bring over your Google Voice number.
If you choose to bring over your Google Voice number, and then three months later decide to stop using Project Fi, you can move your Voice number back to an actual Google Voice account and resume using things as you did before the switch. According to Arscott, this means any of the Google Voice features you lost in the switch, like spam filtering for example, will be available to you again. Common features like voicemail, voicemail greetings, and text messages are all available in Project Fi so you wouldn't have lost these functions to begin with. Also, should you choose to keep your carrier number with Project Fi but still don't want to lose your GV number, you can transfer your Google Voice number to another account, or you can set up Project Fi with another Google account to begin with.