A system comprising: a Service Control Function, SCF, node including a processor and executable instructions configured to be operated by the processor to determine whether a call is a mobile-to-mobile call between subscribers of a telecommunication service provider by: sending a subscriber state request specifying an identifier of a serving subscriber of the call to a Signaling System Number 7, SS7, network, and determining that the call is a mobile-to-mobile call if a response to the subscriber state request indicates success; and a Signaling Transfer Point, STP, node of the SS7 network including a processor and executable instructions configured to be operated by the processor to: determine whether the serving subscriber identifier is included in a routing database of the STP node, in response to determining that the serving subscriber identifier is included in the routing database, communicating with a relay function and responding to the subscriber state request with a default state indicated by the relay function, the relay function being used in place of a subscriber database of the telecommunication service provider, and in response to determining that the serving subscriber identifier is not included in the routing database, responding to the subscriber state request with an error message. a Service Control Function, SCF, node including a processor and executable instructions configured to be operated by the processor to determine whether a call is a mobile-to-mobile call between subscribers of a telecommunication service provider by: sending a subscriber state request specifying an identifier of a serving subscriber of the call to a Signaling System Number 7, SS7, network, and determining that the call is a mobile-to-mobile call if a response to the subscriber state request indicates success; and a Signaling Transfer Point, STP, node of the SS7 network including a processor and executable instructions configured to be operated by the processor to: determine whether the serving subscriber identifier is included in a routing database of the STP node, in response to determining that the serving subscriber identifier is included in the routing database, communicating with a relay function and responding to the subscriber state request with a default state indicated by the relay function, the relay function being used in place of a subscriber database of the telecommunication service provider, and in response to determining that the serving subscriber identifier is not included in the routing database, responding to the subscriber state request with an error message. sending a subscriber state request specifying an identifier of a serving subscriber of the call to a Signaling System Number 7, SS7, network, and determining that the call is a mobile-to-mobile call if a response to the subscriber state request indicates success; and a Signaling Transfer Point, STP, node of the SS7 network including a processor and executable instructions configured to be operated by the processor to: determine whether the serving subscriber identifier is included in a routing database of the STP node, in response to determining that the serving subscriber identifier is included in the routing database, communicating with a relay function and responding to the subscriber state request with a default state indicated by the relay function, the relay function being used in place of a subscriber database of the telecommunication service provider, and in response to determining that the serving subscriber identifier is not included in the routing database, responding to the subscriber state request with an error message. determine whether the serving subscriber identifier is included in a routing database of the STP node, in response to determining that the serving subscriber identifier is included in the routing database, communicating with a relay function and responding to the subscriber state request with a default state indicated by the relay function, the relay function being used in place of a subscriber database of the telecommunication service provider, and in response to determining that the serving subscriber identifier is not included in the routing database, responding to the subscriber state request with an error message.