How to Cancel All Services with Comcast

After the past few days, I've lost absolutely all confidence in Comcast's support systems, and without competent support, there's no point in continuing service with Comcast.  The past few days, except for the tech who came on site, I have seen nothing but absolute systemic incompetence.

How do I cancel my services?  Don't waste my time with retentions.  How do I get in touch with someone who can actually cancel the account?