A method performed by a mobile originated, MO, device in a wireless communication system, the method comprising: transmitting , to a mobile terminated, MT, device , a session initiation protocol, SIP, INVITE request message including information regarding in-call capability features of the MO device , wherein the information regarding in-call capability features of the MO device is included in a contact header of the SIP INVITE request message in a single registration, wherein the information regarding in-call capability features of the MO device is included in a SIP private extension header of the SIP INVITE request message in a dual registration, wherein in the single registration, a Voice Over Long Term Evolution, VOLTE, and a Rich Communication Service, RCS, are registered on a single Packet Data Network, PDN, for a same International Mobile Subscriber Identity, IMSI, or Mobile Subscriber Integrated Services Digital Network, MSISDN, and wherein in the dual registration, the VOLTE and the RCS are registered on a different PDN for the same IMSI or MSISDN; in response to the SIP INVITE request message, receiving , from the MT device , a response message including information regarding in-call capability features of the MT device , wherein the reception of the response message including the information regarding in-call capability features of the MT device is performed based on a determination whether the MT device is the VOLTE device or not, wherein the determination whether the MT device is the VOLTE device or not comprises a determination whether the information regarding in-call capability features of the MO device is indicated in the contact header or the SIP private extension header of the SIP INVITE request message; and performing in-call capability negotiation with the MT device . transmitting , to a mobile terminated, MT, device , a session initiation protocol, SIP, INVITE request message including information regarding in-call capability features of the MO device , wherein the information regarding in-call capability features of the MO device is included in a contact header of the SIP INVITE request message in a single registration, wherein the information regarding in-call capability features of the MO device is included in a SIP private extension header of the SIP INVITE request message in a dual registration, wherein in the single registration, a Voice Over Long Term Evolution, VOLTE, and a Rich Communication Service, RCS, are registered on a single Packet Data Network, PDN, for a same International Mobile Subscriber Identity, IMSI, or Mobile Subscriber Integrated Services Digital Network, MSISDN, and wherein in the dual registration, the VOLTE and the RCS are registered on a different PDN for the same IMSI or MSISDN; in response to the SIP INVITE request message, receiving , from the MT device , a response message including information regarding in-call capability features of the MT device , wherein the reception of the response message including the information regarding in-call capability features of the MT device is performed based on a determination whether the MT device is the VOLTE device or not, wherein the determination whether the MT device is the VOLTE device or not comprises a determination whether the information regarding in-call capability features of the MO device is indicated in the contact header or the SIP private extension header of the SIP INVITE request message; and performing in-call capability negotiation with the MT device . <EOS>