itunes 信用卡問題

請問一下
我剛下載了hipstamatic
結果要把信用卡改回none
卻沒有這選項
然後就說扣款沒有成功的樣子
後來去看了一下明細出現：
we were unable to authorize your payment card for this purchase. please update your billing info

但是app已經下載下來咧??!!
是怎麼回事........................
謝謝!!!!!!!!!!!!!!!!!!!!!!!!!!