The Kenya as well as the South Africa case studies are part of a large, multi-country research commissioned by infoDev about the use of mobile phones at the Base of the Pyramid (BOP), the poorest people around the world. The research program is supported by UKaid, the Ministry for Foreign Affairs of the Government of Finland and SIDA (Sweden).
The South Africa study was carried out by Research ICT Africa and Intelecon and builds on a broader household survey of ICT usage across 12 countries in Africa funded by IDRC (Canada). The report shows that, in South Africa, even among BOP populations, some three-quarters already have phones, but usage of data applications is fairly low. The one exception here is the MXit social networking platform and there is growing use of other social media, notably Facebook Zero. But other applications, such as mobile money, do not seem to be well targeted to the poor.
You can access the Kenya case study here.