Project Fi Carrier Switching

Forcing Carrier Switching:

The phone can be forced to search for service on any of the three by inputting the following dialer codes:

*#*#34777#*#* – Force Sprint
*#*#34866#*#* – Force T-Mobile
*#*#34326#*#* – Force US Cellular
*#*#346398#*#* – Force Next Carrier
*#*#342886#*#* – Resume Automatic Switching

No matter which carrier you force the phone to switch to, the phone will resume automatically switching after two hours.  At this time, this cannot be stopped.

Additionally, these dialer codes may come in handy:

*#*#344636#*#* – Current Network Info
*#*#34963#*#* – Repair a Bad Activation
*#*#4636#*#* – Launch Phone Test Menu

Dialer Code Apps:

FiSwitch is primarily meant to act as an easy way to input dialer codes.  If you are stock, the code will be copied to the clipboard, it will open the Dialer, and if you enable certain settings, be automatically pasted into the Dialer.  All you have to do is hit dial  If you are rooted, the code will be automatically executed upon pressing the button in the app.  The app also comes with a handy widget that presents the three carriers to quickly switch between them.

Signal Spy provides the same dialer code input into the Dialer, although having root will not assist you here; you still have to hit dial.  However, the app displays much more information about the network you are connected to, as well as a network history.

I personally have both.  I use the FiSwitch widget for quickly switching carriers from the Home Screen (while rooted), as well as determining which carrier I am on at a glance.  I use Signal Spy to determine which network and band I am on, as more detailed information is displayed within the Signal Spy app as opposed to just the carrier name on the FiSwitch widget.

Project Fi Coverage Details

General Coverage Information:

The coverage map for a regular FI SIM card can be found here.
The coverage map for a data-only SIM can be found here.

Details about using Sprint:

Using the Sprint portion of Fi is similar to using a post-paid Sprint device.  You have full access to everything that a Sprint customer would while on-network.  This includes their “LTE Plus” deployment, which is their branding for carrier aggregation.  As far as voice is concerned, if you place a call while on Sprint LTE, the phone will drop back to a CDMA connection to place the call.  Sprint does not have VoLTE available to its own customers, so therefore it is also not available to Fi customers.  Additionally, you have access to the same roaming that a Sprint customer would.

PLEASE NOTE: We are in the process of confirming whether postpaid LTE roaming agreements are available to Fi customers.  The remainder of the roaming is available.

Details about using T-Mobile:

Using the T-Mobile portion of Fi is similar to using a post-paid T-Mobile device with one very notable exception.  You have full access to everything that a T-Mobile customer would while on-network, including Band 12, with the exception of VoLTE.  This is a very important differentiation to make because this may present a few issues depending on location:

  • When you place a call on T-Mobile, you will fall back to UMTS or GSM to complete the call.  Traditional T-Mobile users will complete the call without leaving LTE via VoLTE.
  • VoLTE is prioritized at the highest level on the T-Mobile LTE network.  If you use a VoIP solution, such as the Hangouts dialer, your traffic is treated no different than generic internet browsing.
  • Band 12 inherently lacks a circuit-switched voice solution.  ALL voice traffic on Band 12 via T-Mobile is routed via VoLTE.  Since Fi subscribers don’t have access to VoLTE, your phone should fall back to UMTS or GSM.  However, this may or may not happen for a number of reasons.  It is very possible that the call will just fail.
  • It has not yet been confirmed in the aforementioned situation whether T-Mobile will process a 911 call as VoLTE.  The phone is provisioned for it, so it is a possibility.
  • Additionally, Band 12 is being rolled out by T-Mobile to close some of the coverage gap between themselves and other carriers.  There are certain T-Mobile areas in the country that have only Band 12 deployed.  These areas are usually at the fringe of their coverage.  In this case, you have absolutely zero traditional voice service while using T-Mobile on your Fi device.  You will have to either force to a new carrier, or use a VoIP solution to make the call.

The limitations with VoLTE are strictly artificial.  The Nexus 6P is provisioned for VoLTE out of the box, and actually attempts to utilize it even with a Fi SIM card inserted.  The request is knocked down at the network level, as Fi and T-Mobile do not have VoLTE included as part of the deal.  Hopefully this changes in the future because of the above reasons.

PLEASE NOTE: We are in the process of confirming whether postpaid LTE roaming agreements are available to Fi customers.  The remainder of the roaming is available.

Details about using US Cellular:

US Cellular is rather new to the Fi game.  The US Cellular side of Fi is slightly different from what a US Cellular post-paid customer experiences, notably lacking the LTE roaming on T-Mobile (for obvious redundancy reasons).  If you are in a US Cellular native area, you will be able to connect to their LTE network just the same as one of their customers can.  If you place a voice call, you will automatically fall back to CDMA, as US Cellular hasn’t officially deployed VoLTE for even their own customers at this time (they are targeting Q1 2017 for deployment).  It hasn’t been stated whether VoLTE will be available to Fi customers once US Cellular turns it on, but considering the state of affairs with T-Mobile VoLTE, it’s highly doubtful.

The other area where US Cellular shines is actually when you are not in an US Cellular native market.  You have access to the same roaming agreements (sans LTE) as their own customers do.  This means that you have the ability to fall back to Verizon.  Again, LTE is not available from Verizon, but you have full access to their 3G/EvDO network, as well as their legacy 2G/1X network.  With Verizon being the coverage leader in the nation, this is very good.

General Notes about Coverage:

Between the three carriers Fi offers, and US Cellular’s ability to roam on Verizon, you have full geographical access to four of the top five networks in the country.  Additionally, T-Mobile allows roaming on AT&T in some areas where they lack a better roaming partner, so in some cases, you may have access to all five of the top networks through native service and roaming agreements.  All in one phone, with one phone number.  This is HUGE for rural and traveling customers.

International Coverage:

Fi offers international service in many countries throughout the world.  Check out their website here for current details, as this is a continually evolving situation.

Project Fi General Information


Fi currently sells the Nexus 5X, Nexus 6P, Pixel, and Pixel XL.  You can also use a Nexus 6 if you already own one.


Pricing for the service is very straight forward.  The base cost for a single phone is $20 per month for Unlimited Voice and SMS.  Data is charged at $10 per Gigabyte used.  You must have at least one gigabyte included in your monthly plan.  Tethering is also included at the same rate.  The awesome part of the service is that you pay for exactly what you use.  If you use less than the amount of data you select, you receive a refund for the exact unused amount.  If you go over the amount of data you select, you simply pay for the exact amount of extra data used.  No surprises.

Family Plan:

You can add additional phones for $15 per phone.  The additional phones will pull from the same data bucket, and data is charged at the same rate.



Data-Only SIMs:

You can order (multiple) data-only SIMs from Fi for free.  They simply pull from your existing data bucket.  These SIMs are only provisioned for T-Mobile service, and can be used in any device you can shove them into (unlike the full Fi service which requires a Nexus or Pixel phone).  There is a separate coverage map for these SIMs, and they do work in some international locations.

Activation, Phone Numbers, and Porting:

At this time, you cannot port in a phone number from a location that T-Mobile does not have access to a number pool.  It doesn’t matter if you own the number, or if you have the number in Google Voice.  It cannot be done.  Hopefully this changes in the future.