Part of the problem is that getting Comcast to close your account can be a craps shoot. For you, it worked just fine, like it does most of the time. For my mother, it was a nightmare.
My father passed away a few years back and my mother was trying to cut back on expenses, so she went to cancel the Comcast. The account was in my father's name, so she expected there to be some trouble. Comcast required that she bring in my father's death certificate. Also, they would be keeping the death certificate for their own records and a photocopy wouldn't do, so she'd need to go down to the county corner and get a second copy of the death certificate printed and hand signed. While this all seemed fairly onerous, I can at least appreciate the formality from an security standpoint.
After jumping through all of the hoops set forth by the Comcast, my mother drove out to the local branch office and presented the paperwork. The case worker brought didn't know how to handle the situation where someone had actually done everything that Comcast had asked and brought in the branch manager. He then told my mother that they needed my father to personally deliver his own death certificate before they would close the account.