Follow the instructions here to change your payment method for your Apple ID:
- Change or remove your Apple ID payment information - Apple Support
- Payment methods that you can use in the iTunes Store, App Store, and iBooks Store - Apple Support
When entering details for a payment card, be sure to enter your address accurately.
If you still need help, then contact iTunes Support:
(I'm afraid that no-one here can assist you directly. This is a user-based technical support community - you are not talking to Apple here).