Yesterday I got a call from my wife and the iPhone said "Maybe Mrs. SSteve". The phone number was the international version of a U.S. phone number and her custom ringtone didn't play:
Voicemail is also showing international versions of U.S. phone numbers and also shows "Maybe" (normally it just shows the name and no phone number at all):
Contacts isn't formatting phone numbers at all:
Contacts on my iPad still formats numbers the way I expect:
I'm running iOS 12.3.1 on an iPhone 6. I remember seeing recently that there was a carrier update. I must have installed it because Settings -> General -> About doesn't show an available carrier update.
I tried iPhone Contact List Default Country Wrong but dialing *228 says the number isn't allowed.
I tried setting my Region in Settings -> General -> Language & Region away from United States and back but that didn't work. Where else does iOS get the region for phone numbers?