A method, a system, and network elements for transmitting information between a user equipment and an IP packet gateway, are disclosed, the IP packet gateway communicating with an IP network via an interface, wherein, when the UE is requesting at least one service requiring access to the IP network, authorization of the requested service is checked, wherein an error message is sent from the IP packet gateway to the user equipment, when the requested service is not authorized. The present invention discloses several options of signaling error messages between IP packet gateway and UE, for example, via IP layer signaling (e.g. RESV ERR messages) or link layer signaling (e.g. IS2000 and IOS signaling). The solution according to the present invention, in particular, relates to a CDMA network in connection with an IP multimedia subsystem network.