A method, and related equipment, for interoperating between a device (11a) in a first network, such as an IMS network, and a device (12a) in a second network (12), such as a WV network, the first network using a first protocol (SIP) requiring that a message have a request uniform resource identifier including an address scheme, and the second network (12) using one or more other protocols. The method includes a step (41) of converting a message constructed according to the first protocol (SIP) but having as an address scheme indicating a protocol of the second network (such as "wv:") to a message in which the address scheme is changed (e.g. to "sip:") to indicate the protocol of the first network and in which a user uniform resource locator parameter is provided having a value indicating the original scheme, before conversion (i.e. "wv" in the example given).