I want to know why I can not change my region

Your post is like you walking into a doctor's office and asking them why you are sick but not saying anything about why you think you are. Do you see any error messages? Here are my guesses:

This article describes how to change your country setting and the requirements and results of doing this:

Read how to "Change your Apple ID country or region" click here --> https://support.apple.com/HT201389

Here are specific issues and how to deal with them:

● Subscriptions

Make sure you have canceled all your subscriptions ( https://support.apple.com/HT202039 ). However, subscriptions will then still continue until the expiration date. You need to contact Apple and request any ongoing subscriptions you have be ended immediately if you do not want to wait until they expire naturally.

● Spend all your Apple ID balance

One way to zero your balance 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 remainder will get charged to the card.

The other way is to contact Apple and ask them to keep any remaining balance.

● 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.

For items where you need to contact Apple to resolve an issue:

Click here --> https://support.apple.com/choose-country-region/media-services Select your country, then a product. 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:

Contact Apple for support and service --> "See a list of Apple phone numbers around the world." Click here --> https://support.apple.com/HT201232