A messaging server improves interworking of the Group-chat feature (such as defined in Rich Communications Services (RCS)) with short message services such as SMS. It matches chat invitations in an effective manner. When an RCS-User invites an SMS-User to an RCS Group-chat session, the identification of the RCS-User in the Group-chat to the SMS-User is via the MSISDN of the RCS-User. Using the MSISDN of the RCS-User in the RCS Group-chat invitation to the SMS-User will provide a direct match with the RCS-User MSISDN in the address-book of the SMS-User and therefore provide immediate clarity from who this Group-chat invitation was received. The SMS-User can accept or reject the Group-chat invitation by returning the proper response as requested in the invitation.