1. Log in to the 3CX Management Console.
2. Go to Settings.
3. Click Blacklisted Numbers.
4. Click “Add.”
5. There will be two fields to fill out: “Incoming caller ID to be blocked” and “Description.” In the first field, enter the full phone number or caller ID that you want to block. The “Description” field is for you to know why you blocked the number.
6. After you’ve filled the information in, click “Ok” and you’re good to go!