Intermittent Inbound Call Issue - cant hear caller but they hear me

I have a strange problem where sometimes when I get a call I cant hear the caller but they hear me fine. If I make an outbound call back to them there is no issue. There is no problem during a call either and some calls are very long (1hr+). It is not happening every inbound calls just some and it is not one caller but several over the last several days.

I have switched it off and back on

I have updated to latest IOS

The switched it on and back off

None of things worked.

Thanks