1)   Webrequest Callback-Button VoIP-Callbutton
A client clicks on the call-back-button, types in his number, will be called back from the server and at the same time the server calls the website-operator and finally connects them.

 2)   Webrequest Telephonvalidierung VoIP-Webservice
They have a on-line Shop, a forum, a contact stock exchange or a similar Community in the InterNet and place again and again disappointed firmly that people with wrong data announce themselves.