I want to remove my iTunes gift card balance from my account

Buy something more expensive and pay the balance with a credit card or contact iTunes Support and ask them to zero balance your account. See the Apple Support articles below for contact information.   

iTunes Support – world wide   -

Apple Support schedule phone call     -

Billings and Subscriptions   -

Apple on Twitter

Also see

You can’t transfer your Apple Account balance to another payment method. From the article below.

About unused Apple ID balance

You can't redeem or return Apple Gift Cards, App Store & iTunes Gift Cards, or unused Apple ID balance for cash, except as required by law. If your jurisdiction allows for refund of redeemed gift balances, you can contact Apple Support to request a refund. - When you contact Apple, please include the following information:

Your Apple ID.   -

The refund amount.

Your current shipping address.

Apple ID balance - View  *