I'm in the process of closing some web accounts myself. Here's what worked for me:

1. Block all charges or cancel the card, but do NOT issue charge backs just yet (there's no point burning your relationship and I've recently learned that many SaaS share a list of evil charge-backers, so it wouldn't just affect hulu).

2. Send them a registered letter, I always ask to be refunded any charges from after my first support ticket as well as refunded for the letter itself. They rarely do the latter but they always do the former.

But yeah, it's a total hassle and I've come to hate the internet lately...