How Do You Delete Your Credit/Debit Card Information From An iPod Touch?

My friend has an iPod Touch and she wanted to delete her old debit card from her account and use an iTunes card to buy some stuff. Her computer is broken, so how does she go about doing this via her iPod Touch?|||The only way is to connect it to the computer, but since she's using an itunes card, she can just go to itunes store and go to the bottom and tap on redeem and put in the code. Whatever she buys from itunes or the app store on the touch will be bought with the credit until it runs out and not the debit card.|||Ok, so you will have to open up iTunes on the computer, on the iTunes store, there will be a bar of links on the right side of your screen then you will see a link called account, click on it and then put in your password if required, then go to edit payment options, then where you select what payment you want to use like visa or master card, etc, you select none, and then from there you card will no longer be charged.