Actually, there was a company that would take all your bills, call up the companies representing you, and get your bill lowered. They made 10% off that (so if they lowered your comcast bill from $90 to $60, they'd make $3 on it).

There is a name for the practices of cable companies, cell phone providers, and banks - adversarial value extraction.

I'd like to know if this company exists and how to find them. And if they don't exist, why they failed?

If you take away the adversarial part of the idea and don't assume that you have to work against the company, it becomes more profitable. Companies that infuriate their customers would be named and shamed, but shown where their customer service is failing, and how to do better. Mystery shopper companies work on the same principle.

With a company like Comcast, they do not want to do better. Doing better costs money, and it won't make them any money. Their video distribution service is destined to die. Any 12 year old with an Internet connection can distribute video content BETTER than Comcast can (because Comcast is bound by all sorts of silly distribution agreement contracts that restrict what they can do, something that was necessary 30 years ago but not today). And they know your options for Internet access are Comcast or nothing (or next to it with things like DSL and satellite being jokes) in the vast majority of their market.