Mobile phones of network operators T - Mobile and Vodafone are pictured on a desk in Duesseldorf , Germany , 24 April 2008 . The Federal Cartel Office of Germany investigates , for the first time , against the mobile phone branch . Proceedings were instituted against companies that allegedly exploit their market - dominating position , said a Cartel Office spokesperson . The proceedings specificly deal with the difference in prices , when making calls within the network as opposed to out - of - network calls . Critical documents have supposedly been requested of the companies in question . EPA / Federico Gambarini < 저작권자 ⓒ 2007 연 합 뉴 스 . 무단 전재 - 재 배포 금지 . >