As Subscriber Sales, I want to enter a call extension phone number in the least amount of steps necessary, so that I do not create any unnecessary errors

Subscriber user should not need to select country from the drop down, since we know which country the stack is set up in. So the call extension syntax and validation should default to that country. For example, if the stack is set up for NTT in JP, then call extensions should be supported for JP phone number formats and validation.

Remove country drop down selection and default to the country of stack setup.