You'll find them in your routers setup. Open your browser and type in 192.168.1.1 or whatever to get into your router. Now look for ADSL statistics in the menu. You might have to explore the options a bit, since you may be using a different router, but rest assured, its somewhere there.
ADSL providers the world over have minimum required values for attenuation and SNR. If your wiring doesnt meet those requirements, they do not give you a connection. With poor values, interent usually does work, but its just unstable and unreliable, which means fluctuating speeds and frequent disconnections. This obviously leads to customer dissatisfaction, and its something the ISP cant really fix.
You know when you get ADSL for the first time, the guys that come over check these values first. If they're too bad, they'll advise you to get your home rewired in the hopes that they'll improve. On some occasions, however, the values will be fine and so your internet will be fine, but on a later date your wiring may suffer some sort of damage, rendering your internet unstable. This is -NOT- your ISPs responsibility, the wiring is for you to fix.
Lower values for attenuation are good, higher values for SNR are good. For a stable 2mbps connection you'd want an attenuation under 50, and an SNR about 10-12. (My own values are 40 for attenuation and 29 for SNR). If your SNR is under 10 or under 8, or your attenuation is above 50-55, your line isnt very good.
Theres a specific way to wire your house to improve these values. If theres enough interest, I can write up a small explanation. Just bear in mind that the wiring is YOUR issue, not the ISPs.