Virtual cell phone companies that use outside capacity are popular with youngsters and others who don't want to sign long-term contracts.
Mobile virtual network operators, or MVNOs, run a mobile-phone service without actually owning a network. Virgin Mobile USA is a joint venture between British business mogul Richard Branson's Virgin Group and carrier Sprint, whose network is used for the access.
"Achieving a 3 million customer milestone in less than three years since our launch drives home Virgin Mobile's position as a pay-as-you-go pioneer," Dan Schulman, CEO of Virgin Mobile USA, said in a statement on Tuesday. "Our continued growth confirms that we're making a powerful connection with the youth market."
MVNOs such as Virgin Mobile USA target teen-agers, young adults and other people who could find it difficult to sign up with major wireless operators because of their credit histories. Virgin offers a pay-as-you-go plan, which does not require that users sign a long-term contract.
Apart from voice calls, Virgin Mobile's nonvoice data services are popular, Virgin said. According to the company, more than 70 percent of its subscribers used text messaging service and another 60 percent accessed extra content services such as MTV's "Pimp My Ride," THangman, Comedy Central's "Joke of the Day," SongID and Rescue Ring. The MVNO also said that it has approximately 8 percent of the U.S. ring-tone market.