Like I said before, if the voice service is bad, the internet has little chance. If you have a noisy line and the internet is poor, its no use reporting the internet. Concentrate on the voice service. With the current methods of line testing, being automated, it just takes a snapshot of line conditions and presents them on screen as a table of values. Not anywhere nearby, it could be anywhere in the world. If asked nicely, it could take a series of snapshots over a few seconds. This is never as good as a man on site watching an analogue meter for intermittent faults, or doing some meaningful testing with a level measuring set to check for transmission quality, but then again, I might have a biased view on the subject.
It is quite possible that the cable between the exchange and your cabinet was adequate for normal voice frequency, but just wasn't up to high frequencies, so replacing it with an optical link removed the problem.