Very similar experience. I pressed "5" after being prompted to and got their robophone canceller. After listening to a pitch to not cancel, with a long-winded explanation of all the benefits and the chances I'd win one of their drawings, etc., I was able to cancel. But does that make sense? Why is it ok for them to require me to cancel their calling? Nuts!
Gotten two calls from them so far. One at 4:15, the next day at 4:33. I called back because the exchange was the same as where I worked so I figured it was a co-worker. I got the same recorded message "WCA Subscriber blah blah your number *repeats my number* was subscribed on January 20, 2011". I hung up because I didn't know what the hell that was.