Hello Doc1807,
Thank you for posting in the Apple Support Communities. We understand that you received a call from an unknown caller despite having Silence Unknown Callers enabled on your iPhone, and reviewing the Apple Support article Detect and block spam phone calls was a great idea. We'd like to provide some additional clarification.
An unrecognized number might reach you if that phone number is included in your emails or text messages. If you don't want that number to reach you again, we suggest manually blocking it:
Block phone numbers, contacts, and emails on your iPhone, iPad, or iPod touch
However, if this concern isn't resolved, we recommend that you contact Apple Support directly. Depending on your region, you may be able to reach them here:
Get Support
We hope this information is useful. Kind regards.