I am on the same exchange, get the same problems. I've spoken to TelkomZA on these forums and he's told me that the exchange is congested, so we apparently have to wait for Telkom to upgrade the exchange (according to him, they are aware of it and are planning to do so, but he couldn't give me a date).
Damn that is ****e.
I may as well just cancel and wait for the them to sort the issue out.
When i contacted them the woman that helped me told that my exchange is not congested but the main exchange that I we are connected is the problem.
They were gonna try to move me to another exchange but it all just sounds like BS just to give them more time to figure out what the problem is. I am suppose to be getting a call from a technician in the field to confirm if the speeds I am getting is the speeds I will have to live with.