A method of charging a subscriber for using GPRS services provided by a mobile communications network. The method is based on including a flag in PDP activation or modification messages sent from a UE used by the subscriber to a GGSN of the network; the flag indicates whether the PDP context is to be used for signaling data or user data. The flag is examined within the network or at a node external to the network; if the flag indicates that the PDP context is to be used for carrying signaling data, a first charging regime is applied to the subscriber for establishing and using the context and, if the flag indicates that the PDP context is to be used for carrying user data, a different charging regime is applied to the subscriber for establishing and/or using the context.