I have the same constantly high latency, pings and dropped packets.
Logged several faults with Telkom, they just keep signing them off without fixing it. Escalated the issue now, as it has been a constant since November 2012.
If no feedback or resolution within a week, will escalate to ICASA.
Telkom maintains there is no congestion on the La Lucia exchange, so then it must be a line fault that must be fixed. Can't have it both ways.
It's a long and arduous journey....
Same issues here - early evening pings are 30ms - after 9pm pings go up to about 300+ms

So much so that the local gaming server throws you off.
Will try to log a call with Telkom and see what transpires.