why doesn't the region change on my phone?

You need a zero account balance and you need to cancel all your subscriptions. If you have cancelled all subscriptions, but some haven’t expired, contact iTunes Support. You need a credit card issued by a bank in the country the store is in, and you need a billing address in that country. 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. Follow through the screens to get a chat or telephone option.  

iTunes Support – world wide        

Apple Support schedule phone call