We're an entrepreneurial community and here is a case of demand.
Why not meet the demand to cut off internet services?
One idea: create a phone service where I call a third-party (you, the entrepreneur) that connects me to the best number to cancel my service. The third party determines if recording the call is legal and records if so, posting the recording online, along with metadata: date, duration, agent name, locale, etc. If recording call is not legal, still post metadata, or also get all parties' permission to record.
Possibly create script through trial and error to counter their script. Can compile data on agents and supervisors names, can follow up with complaints for agents or supervisors to customer service, etc. Can file complaints with elected representatives, FCC, etc... stuff individuals don't have time for but want to.
Another idea: create a web site that takes subscriber information and mails effective letter, registered if necessary, to best address for service provider, using language to set up legal case if necessary.
In both cases, the company could, over time, compile statistics on each service provider's difficulties, giving some accountability. It could also discover their weaknesses and overcome what individuals might not be able to.
You can probably think of many other ways to attack the problem and satisfy the unmet need.
Might not make huge money, but could create great visibility for the entrepreneur. Then again, it might make huge money too, since so many companies play hardball retaining customers.