I will try to point you in the right direction. Based on your description of Comcast's activities, you have what is called in the real estate world an "easement in gross" and possibly an "easement by prescription." An easement of any kind gives your next door neighbor, utilitiy company, and others the right to enter and exit your your property for a specified use. An easement in gross is often used by utility companies and the like to come onto private property by right of "ingress" (entering) and "egress" (exiting) for a specific purpose.
You should immediately contact a real estate attorney who has a great deal of knowledge and experience in this area--easements in gross held by a cable company--and get good legal advice. Based on my education, although a bit fuzzy now, there are 8 ways to terminate an easement; however, I am not clear how utility or cable companies are truly handled in a case like yours.
"Excessive Use" is the one obvious reason that may apply to your situation and allow you to terminate this easement-in-gross. You should document dates, times, and duration of each entry and exit including the number of people coming onto your property as well as the impact it is having on your life.
I will you luck.