Apple iPhone
Go to Settings -> Mobile Service -> Mobile Data Options -> Voice Options
Disable "VoLTE"
Now you should be able to place calls while outside of the United States.
Are you having trouble making calls while you are outside of the United States of America with your Telgea US-phone number? Try these steps.
Apple iPhone
Go to Settings -> Mobile Service -> Mobile Data Options -> Voice Options
Disable "VoLTE"
Now you should be able to place calls while outside of the United States.