The company has earmarked ZAR5.5 billion ($755.78 million) to build out its Nigerian network, and Nhleko said he expects service quality to begin improving in September. In June, MTN Nigeria paid $150 million for a 3G license, and it plans to have a pilot network up and running by the end of the year. (See Nigeria Awards 3G Spectrum.)

    MTN has also set aside ZAR4.3 billion ($590.9 million) to upgrade its South African network to improve coverage and quality.

    Keeping up with subscriber growth isn't MTN's only concern -- Nhleko noted the company faces logistical and security issues in rolling out networks in war-torn countries where it has operations, like Sudan and Afghanistan. In Ghana, where rollout has gone to plan, MTN has increased its customer base from 2.6 million to 3.4 million since December.

    "The story of the next six months and hopefully far beyond is the rollout," Nhleko said. "I think in a number of these markets we have done a lot now to approve additional capex and, more importantly, ensure that the capacity to roll out the networks and put that capex into the ground is actually there."