True(ly) Awful Voip Quality

I've been a True 1024/512 ADSL customer in Central BKK for the the past 1.5 years, and moved into a new room in my same building about a month ago. I've signed up with True on the same 1024/512 package. My line quality is good, my ADSL never disconnects, and I'm experiencing decent - sometimes great - international DL/UL speeds, although my VoIP quality (Skype & Vonage) is HORRIBLE, with conversations so broken up that it's virtually unusable. It seems to get worse at night (when I need it the most), though occasionally it's just as bad during the day. Here's two tests:

Speedtest.net, which is not too bad:

Though here's the TestYourVoIP.com result:

I've tried it with both my previous ADSL WiFi router as well as a new one, wired and WiFi, and it makes no difference. Given that my DL/UL speeds aren't too bad, and that speeds within Thailand are nearly as advertised, I have a sinking feeling that explaining the latency and packet discards to True tech support will not get me very far. It seems unusual that this happened as soon as I moved, though given that I'm in the same building using the same service, it makes no sense to me.

About 2 years back, I used CSLoxInfo which delivered consistently good service, though since my new apartment has a True phone line, CSLoxInfo doesn't offer service. I've got a 2nd, dead phone jack in here -- does anyone know what I'd have to do in order to get service from CSLoxInfo? Would I need to have TOT activate my 2nd line?