The article Change your Apple ID country or region - Apple Support describes how to change your Apple ID country or region, and the requirements and results of doing this.
You may encounter various issues and here is how to deal with them:
● Subscriptions
Make sure you have canceled all your subscriptions (see: If you want to cancel a subscription from Apple - Apple Support ). Wait for any memberships, pre-orders, movie rentals, or season passes to complete. Items will still be active until their expiration date. You need to contact Apple and request any ongoing items you have be ended immediately if you do not want to wait until they expire naturally.
● Remove all your Apple Account balance
- In the main change country article Apple only proposes a single way for you to clear your balance. That is to contact them and ask them to keep it. Apple offers this specific link for that service --> https://getsupport.apple.com/?caller=kbase&PGF=PGF63005&category_id=SC0998&symptom_id=20198
- Another still viable way is to add a credit or debt card as a payment method to your Apple ID and buy items just in excess of your remaining Apple ID balance. This will use up all the balance and any excess will get charged to the card, leaving nothing in your account.
● From the first link above: "Make sure that you have a payment method for your new country or region." Refer to: Payment methods that you can use with your Apple ID - Apple Support Note that some in that list may not be acceptable to set as a payment method.; for example, account balance. The statement from Apple, and its referring to the link, to me just says that if you were using a payment method in your old country that is not listed in the new country too then you need a new payment method. I do not see anywhere where it says the payment method must be from the same country. I go by what Apple actually says in its online documentation (which is not much and if they have any other restrictions they are not clearly stating them). If it says a method is not valid then you need to try another one until you find one that is. Often using one from the same country is the easiest way to ensure that.
● Pending purchases and refunds
If you have pending purchases, or refunds in the process of being returned to you, you will have to wait until these clear.
● Leave or disband any Family Sharing groups.
Refer to Leave Family Sharing - Apple Support
● Read this support article If your Apple ID or other options are greyed out in Settings —> If your Apple ID is greyed out in Settings - Apple Support
For items where you need to contact Apple to resolve an issue:
Click here ➞ Choose your country or region - Official Apple Support
Select your country (if you do not see your country, also look for "other" regions; e.g., "Other Africa"), then "Choose a product". Click the "show" item under each category for more selections. If you don't see one 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.
or:
See a list of Apple phone numbers around the world. Click here --> Contact Apple for support and service - Apple Support
