I'm having the same issue after the update of One UI this morning. My Sim card has been working just fine before this update. Seems like several people are having the same problem so I doubt everyone all the sudden having bad Sim cards... Mine showing "CallBGprovider keeps stopping", and a black screen so I can't even end the call.
I had to use the WiFi to access my internet to do anything.
The new sim card fixed the call issue too.
Usually best practice after an update is to perform a factory data reset. Has anyone tried that to see if it fixed this? Mine updated, but I haven't had any issues. 😞