High Latency on ADSL for months with no fix

I have been struggling with the same unresolved issue since February. I've called and been told the problem would be fixed several times now with each call having required me to wait for an hour or more on hold.<br> The issue has to do with my ADSL line's latency. The problem seems to occur every night between 7pm and 12am. Which makes things hard because I cannot call Telkom at night and report the problem as it's happening. To counter this I've been liaising with Telkom via Facebook. While the FB service response is excellent, I still have not had my problem resolved in more than half a year.<br> <br> Every night without fail my ping spikes to around 500ms and stays in that range til after midnight - rendering my internet unusable every evening. I have conducted various tests to try and determine the cause of this, including different routers, other ISPs like Afrihost and Webafrica but even with these I have had no luck. At this point I am frustrated and angry at paying for a service that I cannot make use off. Spoken many times with telkom contractors whom all tell me they see no problem despite me stressing repeatedly to each of them that the problem only occurs at night.