I had this same issue with my Galaxy Note 9 and nothing solved the problem, including factory resetting. The issue was absent from the Note 10+ but now resurfaced in the Note 20 ultra immediately after my latest software update.
Try wiping your cache partition, lots of times when you start having issues with a device right after a major update, it is because something got stuck in the Cache. You do this by powering down the phone, then powering it up with the volume up and power/bixby button, hold these until you see a white android. this will then bring you to a boot menu. Using the volume buttons to move up and down, go to "wipe cache partition", select this with the power/bixby button, then select yes, again with the volume buttons to highlight, and power/bixby button to select. After it is done with this task, it will return you to the previous menu, select "Reboot system now" to restart the device. Do this as a test BEFORE factory resetting the device, as this will not loose any data, and MAY correct your issues.
Since I updated to One UI I've had all Kings of glitches and wiped cache partition several times and then took this latest update thinking it might solve some of these issues but it only introduced the phone call issue.