I phoned 311 and was removed within a week or so. What I don't yet know is whether they did what I actually asked: remove me from everything except the snow emergency list. (Snow emergency notification being what I thought I signed up for in the first place, as it was the only thing I could imagine wanting to know about real time, rather than being content to learn about when I read my email. I just hope it doesn't cost me a $100 ticket this winter to find out that no, in fact, they didn't keep me on the snow emergency list.)