As mentioned above the currency depends on the country of your Apple ID. But you can add a sandbox account in App Store connect, sign in with it on your device, and use for texting from Xcode. You can set a country that you need for this test account. Further more, you can add test users to App Store and set the country there. These users can test the app from Test Flight. But in this case they'll have to sign out of the App Store on their device and sign in with the test user credentials.