In a method and system for APN (Access Point Name) correction in a GPRS data roaming scenario where a sponsor operator network is used and a method and system for routing GTP messages to the correct destination network entity after actuating the APN correction as and when required. The GTP filter checks the IMSI and APN data in the GTP layer and, depending on the IMSI and APN data performs APN correction and manipulates GTP parameters to ensure the PDP Context is correctly established between the SGSN and the GGSN, and the further GTP Control or Data messages bypass the GTP Filter application. This solution allows appropriate routing of message, in particular for message to and from smartphone.