I want to reset my app store balance to 0 to change my country

Buy something more expensive than your balance and use a different payment method from the current region for the extra amount; if you can't, click here and ask the iTunes Store staff to zero it.

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I want to zero the App Store balance and change the country

I want to reset my app store balance to 0 to change my country

You need to follow the instructions in the post above yours. Only Apple Support can zero the balance.