How to add money to App Store via iPhone?

I have an iPhone 4 with iOS 6. I can't seem to be able add funds in either App Store or iTunes. I scroll to the bottom of the page, tap my ID, then view ID and there's no where to add money. I have searched everywhere in my appleID settings. The only way to add funds seems to be through redeeming an App Store card and I want to use my credit card. Please don't tell me to add money via my computer, if I could do that I would.

Go to the iTunes application. Fiddle around with the menus, maybe you have to search for something, but at the bottom there should be something like Redeem at the bottom. No device near me ATM so sorry if its in-accurate.

You don't use your credit card to add money, when you want to buy an app/song/movie it just charges that amount to your credit card. I can't remember if they bill you once a week for your total agreed purchases for the previous week. Can't remember if its android or apple that does that or if it has changed. But yea you can't add money to the store, it just gets billed. The only way to add money is like what you originally said about buying an app store prepaid card.

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Every app you purchase will be deducted from your credit card