You might try posting about the situation on the Consumerist blog (it’s owned by Consumers Union, publishers of Consumer Reports magazine).
I’m still having trouble understanding exactly what happened. It sounds from your description like you, the OP were signed up with DirecTV. Then, someone else in the same household signed up with AT&T (which IS u-verse). Keep this simple by just using DirecTV and AT&T as references. There are just the two services in question here. So your household was signed up with two services. Whether you’re using them both or not, as long as the first one never gets a cancellation notice from you, the OP, the customer, they will continue to bill you and you will continue to be liable for the bill.
I think the onus is on the people in the household, and if no one ever called DirecTV to cancel the service, thinking AT&T would do that, it’s not AT&T’s fault. The first time you got billed for both was when you should have been on the phone with DirecTV to make sure it’s cancelled and they don’t continue to bill (and would still need to pay the extra month). As long as both services were delivering live service to the home, as in, you could have switched the feed from one to the other, you are liable to pay both. Did DirecTV ever contact you to collect their equipment or request you return it to a nearby office? If not, they never knew you wanted to cancel service.
So what do you do now? Based on what I can understand from what you’ve written (honestly it’s been a little hard to follow), you’re stuck with the collection. Pay it or let it go to court.