On 24 September 2012 the German Ministry of Finance issued a decree (only available in German language) implementing the principles of the ECJ decision in the “Lebara” case. You can read more of this case here, here and here.
Each sale of single purpose prepaid cards is regarded as a telecommunication service if these cards are sold in the supplier’s own name. Otherwise, if the sale is made in the name of a third person, an intermediary service is on hand. Whether there is a telecommunication service or an intermediary service should be considered on each distribution level.
A single purpose prepaid card in the sense of the decree requires that it can exclusively be used for telephone calls by means of the provided infrastructure, and that it contains all information necessary to make calls.