Cellular networks are connected with each other through a worldwide private, but not unaccessible network, called IPX network. Through this network user related information is exchanged for roaming purposes or for cross-network communication. This private network has been breached by criminals and nation states. Cellular networks are extremely complex and many attacks have been already been found e.g. DoS, location tracking, SMS interception, data interception. Many attacks have been seen in practice, but not all attack are understood and not all attack avenues using the IPX network have been explored. This presentation shows how a S9 interface in 4G networks, which is used for charging related user information exchange between operators can be exploited to perform fraud attacks. A demonstration with technical details will be given and guidance on practical countermeasures.