in my experince, after you applied for a line, you call them and ask to have it converted to an ADSL line..can take up to 21 days...when its ready, they will call you to pick up your router from any telkom shop in SA,
then you go home and install it.
really recommend self install and save yourself R500..as long as you can follow the instructions you will be fine!
you can even call 10219 if you are stuck and they will help you.
whatever speed you choose, i recommend you use Afrihost as your ISP as their normal price per GB is less than half of what telkom charges but you dont get the local bandwidth that telkom gives you.
or you can decide to have an uncapped service and there are a few companies out there that offer that, ranging from Digichill@R300, Sainet@R449, Screamer @R399...but there have been problems associated with them as they are new ISP but maybe getting better.
you can search the threads for more up to date info.
For me the best bet is Afrihost @ R29 per GB and they have monthly specials @ R14-50 per GB!