In July 2008 my son signed up for Xbox Live using my debit card without my permission. i called support and cancelled, but still received charges for months after. I called every month to complain and eventually they said they would mark the account so my son could never sign up using a credit card again.
Guess what, In November 2008 my card starts being charged again. My son had not used the card this time, but had instead signed up using a "free month coupon" he received in a game purchase. BUT, Xbox started charging the same card on his account, the same account they knew darn well had been charged illegally before.
Watch out Xbox Live members. Even if you cancel, you may see the charges start up again months later.
BEWARE OF XBOX, they are ripping people off and illegally charging credit cards.