I use Cybersmart on a Telkom ADSL line.
http://www.cybersmart.co.za/
I was surprised that Cybersmart is actually cheaper than Telkom, even though you still use the Telkom infrastructure. I'm quite happy with Cybersmart and can recommend them with a clear conscience.
One thing is for sure, if I could get this service without the Telkom infrastructure, I would pay more and take it. I try to avoid dealing with Telkom as much as possible. When I do get a line failure, I phone Cybersmart and have them sort it out with Telkom, I refuse to deal with those circus animals directly.