The first time you went to the Contacts screen in the White Calling app, you will have been asked for permission for the app to access your mobile phone’s contacts list.  

If you did not allow this then the app will not be able to access or call your contacts from within the White Calling app.

How do I fix this?

To resolve this issue, you just need to follow these simple steps:

Go to Settings > Privacy > Contacts

Enable the White Calling check button (ensuring it shows green).

Go back to the app and contacts should now be visible. If not, please quit the app and reopen.