The subject matter disclosed herein relates to a method for checking toll transactions, produced from position notifications of a mobile phone connected via a mobile network to a transaction server, with the aid of a network of distributed toll beacons, which can communicate via short-range radio with on-board units of passing vehicles and are connected to the transaction server. To this end, a interoperable multi-functional OBU is created that is formed from a GNSS- and NFC-enabled mobile phone on the one hand and an NFC- and DSRC-enabled OBU on the other hand, which exchange data concerning a session identifier (SID) via their common NFC interface, which session identifier forms a link between the infrastructureless and the infrastructure-bound billing functions of the multi-functional OBU. The disclosed subject matter also relates to a toll beacon and a transaction server for same.