Can't send text to a specific overseas number
I can't send a text message to a specific overseas number.
The message is simply turned down with not delivered notice.
I tried to change the SMS center number but my device, iPhone 6plus, wont' change it. It displays there's something gone wrong.
Sending a text message to other number seems not affected.
Please anyone help me to resolve the issue.
Thanks.
iPhone 6 Plus, iOS 12