A session management function (SMF) receives, from a wireless device, a packet data unit (PDU) session establishment request message. The PDU session establishment request message comprises: location information of the wireless device; and a single-network slice selection assistance information (S-NSSAI) of the PDU session. The SMF selects a local proxy call session control function (P-CSCF) based on: the location information of the wireless device; and the S-NSSAI of the PDU session. The SMF sends, to the wireless device, a PDU session establishment accept message comprising an identifier of the P-CSCF.