nexus - Manually switch carriers Project Fi

I have heard that you can manually switch carriers when using Project Fi. How do I go about this? What is the easiest way?

Edit: Is there an app that does this too?

Answer

You can easily manually switch carriers in Project Fi:

Head into the Phone Dialer app that came with your Nexus phone, then type in these dialer codes to manually switch carrier:

• Sprint = *#*#FISPR#*#*


• T-Mobile = *#*#FITMO#*#*


• US Cellular = *#*#FIDAN#*#*


• Auto = *#*#FIAUTO#*#*

You can also download the Fi Info app, which automates the process a bit with a widget (I use it all the time).

Source and more info.