(Telecompaper) Google is set to unveil its new US mobile service as early as 22 April, the Wall Street Journal reports. The service is expected to allow customers to pay only for the amount of data they actually use each month, rather than buy more than they need in a postpaid plan, people familiar with the matter said. Google's service will run on the networks of Sprint and T-Mobile, the report said. The service initially will work only on Google's latest Nexus 6 phones, and the devices will switch automatically between Sprint and T-Mobile networks depending on which carrier has the strongest signal. The service also is expected to use Wi-Fi networks to route phone calls and data. Google's wireless project has been in the works for around two years. It is part of a broader effort by the company to make it easier for people to access the internet and use Google services.