Is it only the language you wish to change?
Change the language and region on iPhone - Apple Support
"You set the language and region of your iPhone during setup. If you travel or move, you can change the language or region."
1. Go to Settings > General > Language & Region.
2. Set the following:
The language for iPhone
The region
The calendar format
The temperature unit (Celsius or Fahrenheit)
3. To add another language and keyboard to your iPhone, tap Add Language, then select a language.
The article "Change your Apple ID country or region" describes how to change your country setting on everything using your Apple ID, and the requirements and results of doing this --> Change your Apple ID country or region - Apple Support
If you have balance that you wish to remove from your Apple Account. In Apple's support article Change your Apple ID country or region - Apple Support Apple lists only a single way to do this:
"If you still can't change your country or region, or you have less store credit than the cost of a single item, contact Apple Support". Apple offers this specific link for that service --> https://getsupport.apple.com/?caller=kbase&PGF=PGF63005&category_id=SC0998&symptom_id=20198
Apple will remove the balance and keep it.