I'm on my '08 annual vacation in ZA. After the very pleasant main family event (I was actually here for) is over, I had some time with the computer.
The last time I was here I was using 56k, since you needed a real expensive contract for anything faster. Now I'm using 3G.
It is quite simple: You get to buy a prepaid SIM card (without ID *nice*) for about 2 Rand (15 EUR cent), then you buy airtime at any supermarket or vending machine and load it. You can use the same card (or another) to go online directly. This will cost you a plenty of 2 Rand per MB. But you should rather transfer conventional airtime into "Data Bundles". Then you'll pay 189 Rand (~15 EUR) for 500 MB.
The coverage is marvelous and you can achieve everything through SMS (Balance Check, Data Bundle Purchase, Airtime Purchase etc.). The costs are pretty tacky for South African standards. I'd maybe even say discriminatory, since poorer people are going to use prepaid cards and are going to use their phones for internet access. I knew I would have to cut down on VoIP and video, so the costs seemed quite OK for purposes from my european perspective - at first.
Now, if you're running MS Windows with all the apps you probably need (especially Adobe stuff) and have set everything to the "recommended" update features: Get some tissues... you are going to cry. Because after using up the Data Bundle rate, you automatically switch to the conventional rate!
Do not go online without disabling automatic updates. Seriously.
It seems to me that all applications are built for flat rate operation. And tweaking all of these settings requires a certain amount computer experience. I urge you as a developer: Quit the rubbish. People pay for all the marketing messages and useless updates. I urge you as a Web Designer: Do not use flash, downsize your pictures properly, or go without entirely.
Google for instance senses lower bandwidths and sets the UI to "basic HTML". You will have to do it yourself with 3G ;). Still, the whole Ajax magic is quite fair in terms of data volume.