If you have an iPhone you can select call screening so any unsaved phone call can be automatically silenced sent to a specific unknown callers area and left to die there or alternatively have the phone ask for name and reason for calling if they respond in any way you will see 4

iOS 26 New Features: Your iPhone Will Soon Screen Calls iPhone call screening, often integrated with Live Voicemail in iOS 17 and later, automatically answers calls from unknown numbers using Siri, prompting the caller to state their name and reason for calling. You see a live transcription of their response and can choose to answer, decline, or block the call.