Great simple call filtering program for WM Smartphones.
http://www.teog.it/product/download.html
CallFilter is an application that allows to manage your Microsoft SmartPhone incoming calls.
Operating modes are the followings:
* block calls for selected contacts
* block calls for unknown caller ID
* block all calls except selected contacts
* send SMS to Blocked contacts
Manual:
http://www.teog.it/product/manual-en.html