Keeping your payment method up to date in iTunes is essential if you use the iTunes Store to purchase content. Remove, add and edit cards using the Account Info section in iTunes 12.
Remove a Credit Card From iTunes
Step 1: Click the iTunes Store button located beneath the media player at the top of iTunes and then click the Sign In button.
Step 2: Sign in to your account using your Apple ID and associated password.
Step 3: Click the Account icon at the top of iTunes and select Account Info.
Step 4: Click the Edit link located next to the credit card you want to remove.
Step 5: Select None on the list of payment types to remove the credit card.
Step 6: Click the Done button at the bottom of the page to finish removing your credit card.
How to Add a Credit Card
To add a credit card for purchasing from the iTunes Store, use iTunes as well.
Step 1: Sign in to your account, if necessary. Click the Account icon at the top of iTunes and select Account Info.
Step 2: Click one of the credit card providers listed under the Please Select a Payment Method heading. Options include VISA, MasterCard and American Express.
Step 3: Enter your credit card details in the provided fields.
Step 4: Enter the name and billing address associated with the card and then click the Done button to finish adding the card to iTunes.