This feature will allow you to block numbers based on any prefix. For example, if you wish to block all calls from area code 555, simply enable this feature and add 555 to your Group Blocking list.
To add a number to your Group Blocking list, open your Settings from the side menu within the app.
After you have opened the Settings page, select Advanced Settings.
Find Group Blocking, and turn the option ON.
Select the 
icon to add a prefix, then select ADD.
After you have selected ADD, the prefix you have entered will be blocked by NAME ID.
If you would like to remove a prefix from your Group Blocking list, select the Trashcan 
icon.