Here are three ways you can remove all your Apple ID (Apple Account) balance:
1) Spend it:
If your store credit is less than the cost of a single item on the iTunes Store, App Store, or iBooks Store, and you still have a valid payment method for your old country, you can add the payment method to your account [ how to add a card --> Add a payment method to your Apple ID - Apple Support ]. When you buy an item it will first use the remaining store credit and the rest will be charged to the payment method. Perhaps buy something such as a music track which you can download and also keep a backup copy. Remember that anything purchased may not be available for re-download in another country but as long as you have your own copy you will always have it.
2) Ask Apple to keep it:
You can use one of these methods to ask Apple to remove the balance and keep it:
● Click here --> Choose your country or region - Official Apple Support Select your country, then a product such as billing. If you do not see your country, see if there is an "other" listing for that region. If you don't see an option that handles your issue then keep experimenting with selections until you reach one that gets you a chat session or a telephone call and get the representative to redirect you.
● Call Apple Support --> Contact Apple for support and service - Apple Support
● Click on this link and fill out the form if the above two contact options are not available --> Media Services - Contact Us - Official Apple Support
3) Ask for a refund:
According to: Check your Apple Account balance - Apple Support
"If you have an Apple Account balance that you can't use
You can't redeem or return Apple Gift Cards, App Store & iTunes Gift Cards or unused Apple Account balance for cash, except as required by law. If your jurisdiction allows the refund of redeemed gift balances, you can contact Apple Support [use this link --> Apple Support ] to request a refund. When you contact Apple, include the following information:
●Your Apple ID.
●The refund amount.
●Your current delivery address."
Note that this appears to only apply under very specific conditions, to the extent that I have never seen anybody post here claiming they used this method.
References:
Click on this link to read full information about requirements for changing your Apple ID country or region --> Change your Apple ID country or region - Apple Support
