The result: After Telkom was finished mucking about with the upgrades in Feb, I called them and got a very helpful lady on the line who answered all my questions at length, dumb or not.
She undertook to sync my line at 10MBPS and if that was unstable, then back off until reasonable stability was reached. I've ended up with a floating connection speed between 6MBPS and 7MBPS each time I boot my modem. Initially, Telkom's speed was highly unreliable, I read that they were having problems such as congestion etc., but my speed has now stabilised and apart from the occasional drop, my connection is doing very well. Downloads are running at between 600kbps and 800kbps, way better than at the former 5MBPS sync speed.
