iPhone not receiving calls from wife ( and only wife)

iPhone 12 mini ios 17.2.1 will accept calls normally from any other number except my wifes iPhone SE which is on same carrier account.

Only change is I went to Japan for a week ( during which time we facetimed) and returned last week.

Other calls come through.

On my end I sometimes but not always get notification of her call

On her end it may rings twice and then beep beep beep OR it may go to voicemail ( and I get the voicemail notifications.

She can facetime me

She can imessage me

I can call her, facetime her, imessage her- all normal no change.

I have checked blocked caller list ( no)

the dnd is not on

I have deleted her contact card and made a new one

both phones have been started and re-started, wifi calling on and off.

I spent a couple of hours last night with both phones in hand trying to call back and forth.

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When I removed the physical sim card and put it in my old old old iPhone- she could call through as normal.

This suggests the network is fine, her account and etc is fine and the that fault lies within settings on MY iPhone

somewhere

I believe that apple's settings menus are the closest to windows 98 i've ever been.

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Any suggestions for settings to check on my iPhone other than DND, blocked caller and the like.

3rd party spam blocker Hiya caller app is 'off'

thanks, Mike