why is my phone app not working on my iphone?
When I press the phone app on my iPhone, it pops a white screen and disappears, the app is running, but I can not make a phone call
iPhone 6s, iOS 11.1
It is either a software problem that can be corrected by a carrier update on the phone, a restore via iTunes (or a worst an Update via iTunes) or else it is a hardware problem that the Genius Bar can diagnose for you.
You can try to find out which it is by either having the hardware checked or going through the software route.
Since you can make calls from your watch it is not a carrier-related issue at the account level.