Q: I have a iPhone 5c and i cant use my iTunes credit.

Hello imclanahan,

Thank you for using Apple Support Communities. 

I understand that you are trying to use iTunes credit and are being asked for credit card info. You can create an account or edit your account so that it doesn't have a credit card associated. See the following article:

Create an iTunes Store, App Store, or iBooks Store account without a credit card or other payment method

Best regards.