Cant i buy with my itunes balance and credit card?

Yes unless there is also another issue preventing the change. See the following: Change your Apple ID country or region - Apple Support

Another option for your credit balance is also described in that link:

If you can't complete any of the steps, can't change your country or region, or you have less store credit than the cost of a single item, contact Apple Support.

If you have a credit balance, any purchase you make should automatically first use the balance and then charge the remaining amount to your iTunes payment method. It has done that for me in the past.