Don't give Microsoft your card details
Back in the very early days of Xbox Live (on the original Xbox) I entered my credit card details into the Xbox console. Some time before the anniversary for renewal approached, I could see no way of *removing* said card, so to be absolutely sure of cancelling the subscription, I overwrote the card number with zeros (which it allowed me to do), changed the address and indicated wherever I could see, that I didn't want to renew membership.
Around this time I moved house, forgot about Live and never took the console online again.
I got charged an annual membership renewal anyway and ended up spending no small amount of time on the phone to Ireland (I think it was) trying to get a refund. In cancelling my account I had to run the gamut of the hard sell with a Microsoft operative hell bent on forcing me to justify why I was intentionally being such a fool for wanting to leave such a wonderful service. For the record, I don't overly enjoy self flagellation or protestation.
I pay for a gold account on Live once again, purchased DLC etc, but I will never give Microsoft my credit card details. Ever. I rely instead on retail or online purchased payment scratch cards.
This lady was probably a bit of a nerf for not checking, and I find it a bit incredulous that it went on for months without her noticing, but I have a *tiny* bit of empathy for her plight.