Calls fail when settings are 4G, they work when set to 3G
I have a problem that when the iPhone 5s is set to 4G in settings the calls fail. When set to 3G they work fine. It's not the Network as I have another iPhone and that works perfectly on this SIM when set to 4G.
It's like the phone doesn't switch back to 3G to make the call. I've tried restoring and same issue.
Is this a good question?