I am having the same problem as well with my elderly mother calls being blocked. I hope this fix works.
So I started having this same issue with my front door call box, since it's tied to a phone #. It appears to a bug with the S10 and hiya (the spam service), since my wife's S21 is not blocking the front door call box.
Most solutions here to turn off "Caller ID and Spam protection" will work but then you lose Caller ID and Spam protection. I found a good work around. If you go to the play store and download the Hiya app. Then on the app allow any permissions, and when you're in the app Navigate to settings. Under Calls from saved contacts select "Do nothing". You should now be able to get calls from people you add in your contacts.
If you start seeing calls going in through hiya. Go to your settings, default apps, and set your phone app to "Phone (System default)" just leave hiya as default for Caller ID & spam app.
@discodiva: Are the calls from people in your contacts list? If you head to the Phone app > Tap the 3 dots in the top right > Settings > Block numbers > Block unknown/private numbers > Off > Block spam and scam calls > Off, does this help at all. Please be aware that you can remove numbers from your Block list by tapping the '-' symbol to the right of the number.
To further troubleshoot the issue, tap the Back button > Supplementary services > Call barring, and toggle off any active options here, especially 'All incoming calls'.