Also, subscribe to something that doesn't automatically renew. My recent experience is that their cancellation process also has bugs. I had to call twice to cancel, and ended up getting charged for another month.
For monthly subscriptions, you are charged a month in advance. So if your renewal date is the 1st of the month, you'll be charged for November services on October 1.
According to support, if you cancel, the cancellation will be effective 30 days from the date of your call, regardless of when you've paid through. So in the above example, if you pay for November on October 1, and call to cancel on October 2, your service will stop working on November 1 (30 days after October 2), even though you've already paid through November. So apparently if you want to cancel, yet get what you've already paid for, there is only one day on which you should call.