If you’re anything like me you’ve probably been interested in Google’s Project Fi cellular service since it was first announced in 2015. Google hasn’t made it easy to use its ludicrously cheap service, though, restricting it to those with one of a small list of approved devices.

Not wanting to pay for one of the expensive devices Google said you need isn’t going to keep you from using Project Fi–it works in any GSM-compatible device. There is one catch: You need to have a Fi-compatible phone to activate the service. Once that’s complete, you can pop it into any GSM phone and talk, text, and surf away.

Here’s how to get your GSM phone, whether it’s an Android or an iPhone, working on Project Fi.

SEE: Mobile device computing policy (Tech Pro Research)

1. Sign up for Project Fi and order your SIM card

Anyone with a Google account can sign up for Project Fi–just log in and follow the steps. Once you’re finished, you’ll be able to order a Project Fi SIM card (Figure A). Don’t worry–you won’t be billed until you activate service.

Figure A

2. Find a Fi-compatible phone

If you don’t have a compatible device, you’ll need help from a friend, family member, or coworker. Note: The device doesn’t need to be on the Fi network for you to use it, but it does have to be unlocked (see Google’s Fi BYOD instructions for more details).

You’ll only need the device for a few minutes, but you will need to remove its SIM card, insert the Fi card, and sign in to your Google account on the device, so be sure your friend, family member, or coworker is okay with that. You’ll also need to install the Project Fi Android app if it isn’t already present.

3. Install the Project Fi SIM card

Power down the Fi-compatible phone, remove its current SIM card, insert the Project Fi SIM, and power up the device.

Immediately when it powers up, the device should say that Project Fi registration is incomplete (Figure B). Open the Fi app, be sure you’re signed into the Google account you ordered Project Fi service with, and follow the steps in the Fi app.

Figure B

4. Transfer a Google Voice number, or get a new one

As part of the activation process, you can choose to transfer a Google Voice number to Project Fi, or you can get a new number. Choose the option you want (I chose to transfer) and tap Start Transfer (Figure C) or Continue.

Figure C

5. Wait for Project Fi to activate

After you follow the steps in the Fi app, the network will need to activate your device and transfer your Google Voice number, if applicable.

When setup completes, you should see a Welcome to Project Fi screen (Figure D) that shows your number and the status of your data connection. If the screen tells you that porting your Google Voice number may take a day or two just give it time–mine came through in a matter of minutes.

Figure D

6. Test your service and swap your SIM

Make a call, send a text, or browse the web using your data connection to verify the status of your Fi service. You can also see your account details, including data use, in the Fi app (Figure E).

Once you’ve verified it’s working remove your Google account from the device you’re borrowing, power down the phone, remove the SIM card, and place it in your other smartphone.

Figure E

7. Power up your phone and test your service

Turn your non-Fi device on and give it a minute to connect to the Fi network, which your device will likely show as T-Mobile in your SIM settings (Project Fi uses the T-Mobile network in the US).

Once it’s active, Fi Network will show as your carrier on the top of your screen (Figure F), and you’ll be all set.

Figure F

Non-Fi devices lose a few features

Google may let any GSM smartphone access the Fi network, but being on a non-Fi device does have its limitations.

First off, you lose a major perk of Project Fi: Network hopping. A Fi-compatible device is able to hop between Wi-Fi networks, Sprint, T-Mobile, and US Cellular towers to keep its signal strong. Non-Fi devices don’t get this perk and are restricted to the T-Mobile network.

SEE: Google adds US Cellular to Project Fi network (ZDNet)

Second, You won’t be able to access voicemail without calling it by dialing “1” in the phone app. Fi-compatible devices get access to their voicemail in the Phone app, just like those using a regular Google or Apple smartphone, but if you choose to go with Project Fi on a non-compatible device, you’re stuck in the dark ages of dialing in to listen to your messages.

Third, there’s the Project Fi app. It can be installed on non-Fi devices, but when you first launch it, your device will say that its functionality is limited. I’ve been able to do everything I’d want to in the app, such as checking my data use, managing my plan, and the like.

Project Fi on a compatible device might have an edge, but even on non-Fi phones it’s worth it. At just $20 a month for unlimited text and talk, it’s a great deal. Add to that data at $10/GB that you only pay for if you use, and you have an affordable service whether you’re on an officially supported Fi smartphone or not.

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