A method when roaming by a mobile communication device including a SIM card identifying itself using an IMSI roams between a home network and one or several visited networks, which networks are interconnected by a PSTN. The method a) stores on the SIM card a first IMSI associated with a first collaborating network; b) initiates a location update procedure using the first IMSI; c) triggered by the location update procedure and based on the first IMSI, causes an STP (Signal Transfer Point) of the first collaborating network to send a location update message to an ITP (Internet Transfer Point); and d) causes the first ITP to forward the message to an STP of the home network via a wide area network and not using the PSTN.