Join Date: Jul 2009
Location: Los Angeles, Puerto Vallarta, Bangkok, Lisbon
Programs: UA Premier 1K, Amex Plat, GlobalEntry
Posts: 846
Get a Vodafone SIM at the airport.
It's incredibly cheap and the I called the US a lot from safari and didn't spend $30 in two weeks.
I just went to the Johannesburg airport Vodafone shop in mid December and bought the SIM and airtime card and had the clerk load it. Took about 15 minutes total and it included data (email and web).
Steve