Quality One, based in Florida, distributes cellphones and accessories. The partnership gives Yeigo access to the US technology market. Rapelang Rabana, the chief executive of Yeigo, said the shareholding was "multimillion-dollar and significant, but not controlling".
She said the partnership would provide Yeigo with an immediate presence in the US and would allow the local firm to leverage on Quality One's relationships with other technology groups.
"[This partnership] now provides us with our desired global platform for greater access to new markets and the capacity to conclude major licensing deals," she added.
Quality One's president, John Chiorando, said in a statement this week: "Differentiation and value-add, through new services such as data recovery and inexpensive conference calling that can be fully integrated on the Yeigo platform, will be pivotal for players in the global telecoms arena.
"By partnering with Yeigo, we are guaranteed to receive evolving innovation that keeps up with the high demand of these users."
Yeigo was founded in 2005 by Rabana and two other University of Cape Town graduates, Lungisa Matshoba and Wilter du Toit.
The company saves users money by directing their voice calls through the internet through wi-fi hot spots or the operators' data networks, rather than over the voice network. The only cost incurred by a Yeigo user is that of connecting to the internet.
Calls made through a wi-fi connection could be totally free to the user in a freely available hot spot. In addition, a Yeigo user who calls a non-user will enjoy substantial savings on the cost of calls.
Rabana said that since its launch last year, the company has spent most of its time on research and development.
It plans to license the software platform to other major players seeking to provide cellphone VoIP calls.
Last year the technology firm launched Yeigo Lite, which is compatible with most cellphones that support the Java platform. Yeigo Lite provides some of Yeigo's functions, such as cost benefits for international calling, short messages and free instant messaging.