Go to your iPhone's "Settings" app. Select "Phone." Scroll down to the "CALL SILENCING AND BLOCKED CONTACTS" section. Toggle on the "Silence Unknown Callers" switch. With this feature turned on, calls from numbers that are not in your contacts list will be automatically silenced and sent straight to voicemail. This can help reduce the number of unwanted calls that you receive, allowing you to focus on the calls that matter most.