See Payment methods that you can use with your Apple ID - Apple Support. If he is already using the card with his Apple ID it might not be possible to connect it to another account, or it may be that Apple won't accept a card in someone else's name.
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See Payment methods that you can use with your Apple ID - Apple Support. If he is already using the card with his Apple ID it might not be possible to connect it to another account, or it may be that Apple won't accept a card in someone else's name.
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Why won’t Apple Music let me add my debit card
