Your region and currency is automatically selected when signing up based on your location and number used to sign up.
If you have moved to a different country, you can continue using the same account. You can update your contact details but changing the currency on an existing account is not possible.
You can choose to create a new account in the region/country you have moved to which will give you the same currency as per your new location. Make sure to redeem your Reward points on your current account as the points are not transferable.