Everybody with a German phone number (Germans, and everybody else that obtains a German VOIP "landline" phone number) can call free to landline phones in Austria, Canada (including mobile phones), Denmark, Germany, France, Italy, Netherlands, Poland, Switzerland, Spain & USA (including mobile phones) via a service called "Peter zahlt" (Peter is paying). This service is not limited to VOIP phones, because it is only initiated via web. The company is adding new countries every month. The service is at the time operational every day from 6: oo to 24:00. Peter zahlt is generating its revenue from advertisements which are shown within your internet browser while you are talking. You are of course free to close your eyes, turn off your monitor or move elsewhere. In other words: The advertisements are not annoying. Their must be a catch: Not really. You have to initiate the call via an internet browser. Your calls are paid by visual advertisements on that particular webpage while you are talking (you are not obliged to look at the advertisements - just close your eyes ;-)) and the time for one phone call is limited to 30 minutes (you are free to call as often and frequent as you want). No registration is needed. Just type both phone numbers into the browser window and talk for free.