I am having the same issues as mentioned by previous posts for my exchange on 021-424-XXXX.
I also just received a call from Telkom after I lodged a ticket with them two days ago. The Telkom agent dialled down my ADSL line speed from 8Mbits all the way back to 4Mbits while on the phone with me as we were testing the results, but unfortunately without any positive effect. The end result is still a measly throughput of between 0.1-0.2 Mbits with latency from Cape Town to Johannesburg between 800-900ms.
It has to be said however, that my line speed synched to 8Mbps after the upgrades were rolled out on Monday without a problem and I received up to 6.5 Mbps line speed for at least 1.5 days after that before it all went pear-shaped. This and the aforementioned testing implies that the issue is not merely due to incorrect line speeds in relation to the distance from the exchange.
Therefore it strikes me that Telkom themselves are not quite certain where the problem is at present and this fault might take a while longer before it is remedied.
Update: I just received another follow-up call from Telkom and they have informed me that they are looking into the DSLAM in my area. The agent assured me that I should receive another follow-up call tomorrow to test the results of that outcome. Ergo, this correlates with what doc_msk has posted, and it would seem that Telkom screwed up a number of its DSLAM upgrades during this trial phase.
Also, I reckon since I am paying for their highest speed ADSL and I am currently getting worse than modem speeds, that Telkom should credit me R18 for every day that goes by in which I don't have the service I am paying for. Who's with me on this?