Call charge fraud in connection with data or telecommunication services involves transferring the cost of telephone calls or data transfers to a third party. A PBX system can be manipulated in various ways from the outside. On the one hand, attackers can try to abuse existing features for call charge fraud. These features include, for example, remotely reprogrammable call forwarding or dial-in options. On the other hand, rights can be granted in such a way that incoming outside lines occupy outgoing outside lines. In this way, the caller can be automatically reconnected to the exchange from the outside when dialling a specific number— but at the expense of the PBX operator.

Along with external attackers, employees within an organisation can also be involved in call charge fraud. For example, they can try to make calls at the expense of their employer or other employees, such as by making calls from other people's devices, obtaining other people’s authorisation codes (passwords), or changing personal authorisations.