First time poster here. I work for one of the large accounting firms as an auditor. Reading between the lines, I wonder if there is something going on that is not being captured in the article. Let me play devil's advocate for a minute.
Accounting firms are held to strict independence rules. Some are very black and white, and include not investing in the companies you audit, not having loans from them, not performing certain services outside of audit, etc... Other rules are more grey, such as being independent both in fact and in appearance. It can be interpreted based on the situation. The intent of the rules is to ensure that the relationship between auditor and client is as objective as possible. Doesn't always work 100% since any rule can be circumvented if you try hard enough, but that's the intent and it gets you a lot closer than not having the rules at all.
If you call up the company's Controller (who usually reports directly to the CFO) and start trying to throw around your weight and that of your firm, it's not hard to make the case that you are in violation of independence rules. Even if the customer was not being belligerent, if I were the Controller, the first person I'd call is the partner to ask why some peon is calling my office over a billing issue. Who does that? Nobody, that's who.
If he was being belligerent, which is entirely possible since we all know how frustrating Comcast's customer service is, that's a major problem. It's a pretty easy call for the partners to cut him loose. Independence issues are taken seriously, and nobody wants the regulatory bodies investigating their firm over something so trivial. Was he being obnoxious? Who knows? Did he throw out the name of his firm? Again, without recordings nobody knows.
As a side note, the PCAOB does not investigate companies like Comcast, as is implied in the article. They are the oversight board for the accounting firms that audit publicly traded companies. Either Conal is not very knowledgable about his profession, or the author has his facts wrong.