Project Fi provides an innovative new way to provide wireless service across multiple carriers. At this time, Fi utilizes Sprint, T-Mobile, and US Cellular as carriers. The phone should automatically select the best carrier based upon location, however most reports indicate a strong preference for T-Mobile. This is one of the most interesting and groundbreaking wireless services to have come about in recent memory. No other service can currently provide access to three of the top five carrier’s networks, all with one phone number and one SIM. Given the intricacies of this, the pages below may help better understand the ins-and-outs of the service.