Unknown caller ID

I have recently gotten a fair phone 6+ and have run into what seems like a long time issue where anyone calling me shows up as “unknown” with no number attached so I can’t call back. This seems to go away when I turn off 4G calls. Is there any other way of sorting this out? I am in Ireland and I don’t see my country even listed on the list of compatible phone networks…

Hello
Please let us know your provider.
It seems to me that this issue is especially acute for some providers.