Check Media & Purchases
Your Apple Account’s country or region determines which App Store storefront you see. Your device language and regional format are separate from your store account region. Changing the interface language to English does not change where the app is available for purchase. After opening the product page, check its availability in the App Store.
Go to Settings → Apple Account → Media & Purchases → View Account → Country/Region. You may be asked to authenticate, and labels may vary slightly between system versions. Check which account is used for Media & Purchases, not just the account name shown at the top of Settings.
To find the official option for changing your region, go to Country/Region and select Change Country or Region. This section only explains where to find the option. Whether you can complete the change depends on factors such as your account balance, subscriptions, payment method, and other conditions shown by the store. Review each system prompt before proceeding.