Google opened up its first smartphone service called Project Fi that depends on Wi-Fi hotspots to connect, and it's now offered to customers in the U.S.

Instead of creating its own mobile plans, Google made a collaborative effort with Sprint and T-Mobile to offer its customers a cellular service.

The company is determined on two important selling points concerning the service of the Project Fi such as the monthly billing and flexible service.

A user can connect between service switches through a Wi-Fi network or cellular service depending on signal strength.

Where Google shows that about 50% on clients of Project Fi use Wi-Fi network connectivity more.

While traveling abroad, customers would be able to use their Project Fi mobiles but still pay the actual price for data, depending on the country, cell coverage when connected through a mobile carrier would cost 20 cents per minute and a shifting rate when talking over a Wi-Fi network.

Project Fi's standard service cost $20 a month for talk, text and Wi-Fi ties, while it covers 120 countries for international coverage. And for cellular data, Google prices a flat charge of $10 per GB.

Project Fi's phone service also offers its customers a purchase of a data-only SIM card that shares the same data budgets to be used with their smart devices, where they can attach nine SIM cards onto their accounts and use them in different devices. As for the company's mobile plan charges a user at a flat cost of $10 per gigabyte for data while the cost of unused data will be paid back to their accounts.