How to Cancel an iTunes Account
Whether you want to stop yourself or your child from constantly downloading songs, television shows, movies or audiobooks through an iTunes account, you may want to disable it to prevent future downloads. Consider these methods to cancel an iTunes account or hinder its future use.
Contact Apple customer service by sending an email through the Contact Us link at the bottom of the Apple.com iTunes support page. Let them know you want to cancel an iTunes account and they'll contact you for further information. However, note that if you choose this option, it may also hinder your ability to access the purchases you've previously made, particularly on computers that weren't authorized before you cancelled the account.
Try to cancel an iTunes account by eliminating the ability to access it on your computer. Log into iTunes and pull down the Store menu. Click Deauthorize Computer and enter your iTunes account password to disable the use of iTunes on your computer.
Disable the credit card option without having to cancel an iTunes account if you just want to temporarily stop charging purchases or prevent someone with access to your computer and password to download songs or videos. Just access the Account Information page, click Edit Credit Card and choose "None" and "Done" to remove your card number.
Consider simply changing your password frequently if you'd rather not cancel an iTunes account completely, but want to lock someone else out from making purchases on your credit card. Since you'll be creating new passwords often, however, be sure to write it down (somewhere where only you will see it) so you won't forget.