how to stop Xfinity e-mail account?

The holder of the account has died, is no longer a Comcast subscriber, and it's time to terminate their Xfinity e-mail account, which is just receiving spam now. There are MANY online requests for instructions on how to do it, with answers by allegedly knowledgeable people, and none of their methods work. Anyone out there want to try? Kind of stunning that it seems to be so hard to do.