Google’s upcoming mobile carrier service has been revealed in a leaked Android app, providing some interesting details about its upcoming mobile service. The newly discovered app, dubbed as ‘Project Fi’, suggests that Google’s mobile customers will get free calls and texts in the U.S, and will only be charged for data services they actually use. According to a report by Android Police, Project Fi is the codename given for Google’s Mobile Virtual Network Operator (MVNO), and was included in a Tycho app that was spotted running on an unofficial build of the Nexus 6. The app code points to ‘Nova’, the rumored name of Google’s MVNO service, looking very similar to apps from other carriers.

Project Fi is being built around the idea that customers only pay for what they use. It will include service plans like any other carrier, but in an event if customers do not fully utilize the data allotment they have chosen, the unused amount will be credited back to the customer at the end of the month. In case they exceed that particular amount, they will be charged the same flat rate for each extra gigabyte.

Put simply, Google is currently planning to charge customers as per data usage. If you only need a gigabyte of data, you just pay for one. In case you need more, Google will sell you extra gigabytes as per your requirements, making it a ‘pay as you go’ service. Though we’re not clear as to whether Google will have a monthly billing cycle or just let you pay as needed for data. Meanwhile, earlier rumors also suggested that Project Fi would only be compatible with Nexus 6 at launch.

As we have seen in the past, Google will also be monitoring customer’s call history and sell it to advertisers to target better ads. The exact release date of Project Fi to the public still remains unclear, though we should get more information about Project Fi during the Google I/O developer conference. Google usually unveils new products and services at its I/O developer conference, scheduled for May 28th and 29th