I tried to cancel my membership, but there's no way to do it online without giving them a call. They won't pick up if you call, you have to press 1 and 1 again to get a callback.
Shady and left a bad taste in my mouth. Would not try again.
CLEAR wireless is the same way -- I signed up online, used it for two months, and attempted to cancel. I couldn't cancel online (even though I signed up online), and I couldn't reach anyone when I called -- after waiting on hold 20-25 minutes each time. I finally called my bank and they cancelled my card and blocked CLEAR from charging my card; I'm not sure if that's something that's available for you to do so, but, that's how I needed to resolve a similar situation.
Shady and left a bad taste in my mouth. Would not try again.