There's only one easy way to cancel service with a company like Comcast. You have to lie and tell them you're moving to a city that they don't serve. They don't transfer you to customer retention and you'll be off the phone in a few minutes.
Sure, you should be able to cancel on the phone with no hassle but that is a pipe dream. This is one instance where the old-school method still works best. I've done this with Verizon & Sprint when I lived in the States and was even able to cancel without penalty (they raised SMS a few cents each time) and not deal with their retentions people.
Now it is my preferred method for anything that takes over 10 minutes on the phone. Even if they are on the line, 10 minutes is a hard cutoff and I hang up, type a short letter, and mail it. It's low-tech but very effective.
And for anyone else with Comcast, here's the fine print that Ryan should have read to save all this aggravation. Scroll down to section 9 b (1): https://www.comcast.com/Corporate/Customers/Policies/Subscri...