cannot change my country/region?

You need to cancel all your subscriptions. If you have an account balance, either buy something more expensive and pay the balance with a credit card or contact iTunes Support and ask them to zero balance your account.

Purchases - View, change, or cancel your subscriptions

Purchases - Subscriptions not billed through Apple 

Region - Change your iTunes Store, iBooks Store, or App Store country or region

If necessary, contact iTunes Support. Either use the form or scroll to the bottom of the page in the 2nd link. Follow through the screens to get a chat or telephone option. 

iTunes Support

iTunes Support – world wide

You can

1. If you live in the country you are changing to with billing address & credit card issued for that country.
2. You do not have balance in the account with the previous country.