You can also pay for this order by redeeming an iTunes Gift Card. Please see this page for more information:
http://support.apple.com/HT201209
If you choose this option, after you redeem the code, the unpaid balance of the order will be deducted from your store credit balance.
I hope this helps. Let me know if you have any other questions, I’ll be here to help. Take care, Pipat.
Sincerely,
Lovely
iTunes Store Customer Support