xbox live credit card need help

OK, so I am trying to remove a credit card from xbl because it charges you automatically to auto renew your 12 month subscription and I'd rather go back to the pre paid cards.

I read HERE that you can remove the card by changing your payment method to a made up credit card which doesn't exist. I am just wondering if when the time comes round for my subcription to auto renew, xbox live will be unable to charge the card and then like suspend me or something? Or if they will suspend me when the expiration date i enter for the fake credit card is reached.

Anyone able to offer a hand?

This is probably a long shot, and it might sound dumb, but you might try changing the exp. date on your current card to now (10-07). egraves7

I just tried that and it said it can not be authorised or something?

This is probably a long shot, and it might sound dumb, but you might try changing the exp. date on your current card to now (10-07). egraves7

I just tried that but it said it couldn't be authorised and it says that whenever I try to enter details for a fake card.Someone please help me