I know it sounds weird.
Device: Xperia XA2, SOS: 3.4.0.24

Fact is, I have been getting reports of people not getting through to me or phone call quality being very bad.
The other day, a call also cut out, twice, after just a few seconds. I put the SIM card in another phone, and we had a long coversation after that.

Now I think somebody mentioned that they had problems with international calls only...?
It is quite possible to be so in my case, too. At least I never noticed any problems with domestic (Finland) calls.
I found a post that might explain/corroborate this, but of course I have no idea about what is really happening here.

Can anybody confirm, or explain?

This is probably totally unrelated but I had random "SIM card removed" popups on Xperia X all the time. The truth is, it was a prepaid SIM that I allowed to expire so I did not know whether it was my phone or the network disabling the card remotely. I threw it away and never put a new SIM in, so I will never know.