You can configure NumBuster to automatically block messages from phone numbers added to your blocklist as well as from all unknown contacts.

SMS blocking setup

1. On the NumBuster home screen go to Settings.
2. Select the option Blocking settings.

3. Activate the SMS blocking switch for phone numbers from your blocklist.
4. Activate the Unknown numbers switch to block SMS from phone numbers not in your contacts.

How to unblock SMS

To cancel blocking tap the switch next to the required option to make it inactive.