Whitelist Call Blocker is a call blocker, with that you can determine which callers reach you. So it is possible with activated Whitelist Call Blocker, that for example only the group "family" can reach you. All others only hear a busy signal. Of course, your phone will not ring if the caller is not a member of an allowed group to call you.
By working with groups there are only a few clicks to block or allow hundreds of callers by Whitelist Call Blocker.
If the blocker is not working in most of the cases the local phone number format is the reason.
So if you want to get it fixed soon please send me the exact format of the number as it's to be seen in your display when somebody calls you. And tell me your country you are from. You can even write the numbers as an X (e.g. ++XXXX XXX XXX or XXX XX XXX X) Important for me are spaces and the non digits and the length.
Please report errors to firstname.lastname@example.org or on my facebook site at https://www.facebook.com/whitelistcallblocker