If you are being seriously bothered by unknown callers, you can make use of the “Silence Unknown Callers” feature and “Do Not Disturb” mode to Allow Calls only from Known Contacts on your iPhone.
When “Silence Unknown Callers” feature is enabled on iPhone, it allows calls only from those callers who are already listed in your Contacts List, which automatically results in all Unknown Callers being blocked on your iPhone.
If unknown calls are still reaching your device, it means that someone is calling your device with a hidden caller ID, which can easily bypass the “Silence Unknown Callers” feature. In such cases, you can make use of “Do Not Disturb” mode to effectively block all unknown callers, including those who are hiding their phone numbers.
Allow Calls Only From Known Contacts On iPhone
In most cases, you should be able to prevent unknown callers from bothering you by using “Silence Unknown Callers” feature, which is easy to use and has been specifically designed to allow calls only from known Contacts.
If you are still being bothered by an Unknown Caller using a Hidden Caller ID, the most effective way to block such Callers is by configuring the Do Not Disturb mode on your iPhone to allow calls only from those that are listed in your Contacts list.
1. Enable ‘Silence Unknown Callers’ feature on iPhone
As mentioned above, the easiest way to block unknown callers on iPhone is by enabling ‘Silence Unknown Callers’ feature on your iPhone.
1. Go to Settings > Apps > Phone.
2. On the next screen, scroll down to “Screen Unknown Callers” section and select the Silence option.

After this, your iPhone will only allow calls from known people that are listed in your Contacts list and silence all unknown callers.
2. Allow Calls From Known Contacts Using “Do Not Disturb” Mode
As mentioned above, the “Silence Unknown Callers” feature can be easily bypassed by anyone that is using a Hidden Caller ID.
Hence, the most effective and fool proof way to Allow Calls only from known Contacts on iPhone is by using “Do Not Disturb” mode.
1. Go to Settings > Focus > Do Not Disturb and tap on the People Tab.

2. On the next screen, make sure Allow Notifications From option is selected > tap on Allow Calls From and select Contacts Only option in the pop-up menu that appears.

After this, whenever your iPhone is placed in “Do Not Disturb” mode, it will allow Calls only from those who are listed in your Contacts List. All other Calls from unknown Callers will be automatically silenced and diverted to Voicemail.
If you have numerous Contacts, you can select the Favorites option and this will allow calls only from those who are marked as favorites in your Contacts List.

Note: While this method is very effective in blocking unknown callers, it can make you miss valid Calls from people who may not be listed in your Contacts List.