If you mean that you want to charge them to your account with your phone's carrier then you can't - you can only pay for iTunes purchases from your iTunes account, so you need to put a credit card on your account.
If you don't have a credit card then there are instructions on this page for how to create a new account without giving credit card details : http://support.apple.com/kb/HT2534 - though if you want to download paid-for items you will need a payment method on your account.