iPhone 11 blocking calls from unknown numbers on iOS 18

Yes, that’s a relatively new feature that you can enable and disable. Please follow this path,

iPhone > Settings > scroll down > Apps > Phone > scroll down > Silence Unknown Callers > disable, if it is off, momentarily turn on and then off again.

Perhaps you have Silence Unknown Callers turned on.

• Open Settings App
• Scan to the bottom and tap Apps
• Find and tap Phone
• Turn off Silence Unknown Callers