WebEx XML API create user account for meeting

I'm using XML API to create meetings, and i want to also create user accounts for that meeting so that user can just click on join link and get in (without the need to register). There are two options from what i can see in documentation, CreateMeetingAttendee which only adds user details to meeting without sending mail to that user with join details, and RegisterMeetingAttendee that updates user status and sends email notification. I'm scheduling meeting like this:

public string CreateMeeting(string name, string password, string start, string duration, string registrationNeeded)
{
    var xmlAuthBodyContent = new StringBuilder()
        .AppendLine("<bodyContent ")
        .AppendLine("xsi:type="java:com.webex.service.binding.meeting.CreateMeeting">")
        .AppendLine("<accessControl>")
        .AppendLine("<meetingPassword>" + password + "</meetingPassword>")
        .AppendLine("</accessControl>")
        .AppendLine("<metaData>")
        .AppendLine("<confName>" + name + "</confName>")
        .AppendLine("<agenda>" + name + "</agenda>")
        .AppendLine("</metaData>")
        .AppendLine("<attendeeOptions>")
        .AppendLine("<emailInvitations>true</emailInvitations>")
        .AppendLine("<registration>"+ registrationNeeded + "</registration>")
        .AppendLine("</attendeeOptions>")
        .AppendLine("<participants>")
        .AppendLine("<maxUserNumber>3</maxUserNumber>")
        .AppendLine("</participants>")
        .AppendLine("<enableOptions>")
        .AppendLine("<chat>true</chat>")
        .AppendLine("<poll>true</poll>")
        .AppendLine("<audioVideo>true</audioVideo>")
        .AppendLine("</enableOptions>")
        .AppendLine("<schedule>")
        .AppendLine("<startDate>" + start + "</startDate>")
        .AppendLine("<openTime>0</openTime>")
        .AppendLine("<joinTeleconfBeforeHost>FALSE</joinTeleconfBeforeHost>")
        .AppendLine("<duration>" + duration + "</duration>")
        .AppendLine("<timeZoneID>25</timeZoneID>")
        .AppendLine("</schedule>")
        .AppendLine("</bodyContent>");

    retu Request(xmlAuthBodyContent).SelectSingleNode("//*[local-name()='meetingkey']").FirstChild.IerText;
}

Any help is appreciated.