Ringer has red slash though it but all ringer settings seem to be on

Hi. I'm helping a friend who has a fully updated iPhone 6S. He is in a foreign country.

The problem is when he receives a call, ringtones will not sound alerting him to the call. Vibrate works but ringtones don't. The phone had worked fine until sometime after when he switched to the foreign country sim.

If he raises the volume with the physical volume button, on the screen it shows "Ringer" and the level rises but there is a red slash through the bell on the left indicating the ringer is off.

The physical Silent Mode switch on the left side of the iPhone is set to off - it is in the up position with no red showing. If he goes into Settings/Sounds, Vibrate on ring is on, Vibrate on silent is on, and below that, under Ringer and Alerts the volume is set all the way up and change with buttons is selected.

It seems that with the settings set like this the ringtones should work but they don't. Also like I said, on the screen when you raise the volume, it has the slash through the bell.

Is there a setting I'm missing that would cause this?

I've forced reset the phone and we also did a complete wipe and restore from cloud and issue persists.