Boku last week announced it secured $13.75 million in venture funding to expand carrier billing across numerous carrier connections in developed and emerging markets worldwide, according to a press release.

Several of Boku's existing venture investors from Silicon Valley have followed on with their investments in Boku, including Khosla Ventures, Benchmark Capital, NEA, Index Ventures and DAG Ventures, in addition to other new and existing investors in the U.K., U.S. and Asia. This new portion of venture funding, which was oversubscribed from Boku's initial financing plans, brings the total amount Boku has raised to $91 million since its founding in 2009, according to the announcement.

"Early on we saw an opportunity with Boku to provide a digital payment solution for the hundreds of millions of people who don’t have access to bank cards or credit cards," said David Weiden, who is a Partner at Khosla Ventures. "Carrier billing has now moved beyond this to become the preferred alternative payment method for many of the world's largest merchants."