What can I do about my horrible DSL service?

My DSL randomly stops working every other day or so, and is dead for hours at a time - or sometimes longer - for no apparent reason. When I try to manually reconnect, my router tells me it can't get an IP address from the PPoE server. Then, a few hours later, it starts working again as abruptly as it stopped.

I've done all the standard things (checked filters on the jacks, etc), and have had your tech guys come to my house twice already. Both times they confirmed that everything was working OK inside, and that the problem was most likely at the main box down the street. Both times they claimed to have fixed the issue after checking , and it seemed that things did indeed work better - for a week or so. Then the random outages resumed.

Your infuriatingly bad customer support has yet to provide me with any helpful information. When I call, and am finally able to reach an actual human (usually after waiting 20 minutes, being disconnected, or both), all I get is someone following a scripted set of inane questions like "What kind of computer are you using?". When they run tests on the line, they tell me that everything appears OK.
"The problem is probably on your end, so please check your filters again sir."

The bottom line is that you simply aren't providing the service I'm paying for, which is functional DSL.

What can I do?

Can I, like, take you to court or something?