The European Commission has slammed both O2 and Vodafone for charging foreign mobile users too much when they "roam" on the two companies’ mobile networks in Germany.
The commission said both had abused their market position over several years up to "at least the end of 2003", during the charging period studied.
The amounts charged for foreign roaming users were far too high when compared with German users from other networks who were also roaming on the pair’s networks, it said.
The commission now wants assurances from O2 and Vodafone that the much higher difference in charges will end.
Similar demands were made of the same two operators in relation to their UK networks last July.
UK regulator Ofcom ordered all UK mobile operators to reduce their domestic charges for calling a different network last year, so it would be cheaper, for instance, for an Orange customer to call a Vodafone user.