Truphone, the British VoIP-on-a-handset firm, has raised another £16.5m to fund its transformation into a grown-up telecoms company.

The Series B round comes from private VC investors, with all Truphone's existing backers stumping up more cash. The company raised £12.5m less than two years ago.

Truphone has setting its sights on becoming a primary provider, where it owns the entire billing relationship with the customer, as opposed to being a back-up service for making cheap calls. .

Truphone's VoIP service is software based: you install the free app onto your mobile and away you go. It operates over Wi-Fi connections when available, and bounces customers back to their existing operators when they are more than hundred yards from a hotspot. But with the assets of SIM4Travel, bought last week, Truphone aims to be the only operator a customer needs globally. Calls go over Wi-Fi when that's available and over partner GSM networks when it's not, with all the billing coming from Truphone.

"We aim to provide ultimate price and convenience, wherever you are. One world, one SIM," reads the statement from CEO James Tagg. "Beyond that, as a 'Voice 2.0' company we can start to develop and introduce new internet-based features and applications that give customers a richer mobile experience."

The investors will, no doubt, hope that a "Voice 2.0" company makes more money than most of the "Web 2.0" companies whose game is to be bought by someone bigger before their backers run out of patience. ®

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