pass arguments with called service

edit

Hey, in my code I call a service that calls another service

bool srvCallback_my_switcher(cob_srvs::Trigger::Request &req, cob_srvs::Trigger::Response &res)

{   
    if (client.call(srv))
    {
        srv.request;
        stuff..

    res.success.data = true;
    return true;
}

is there a possibility to call the service srv with an argument for example a bool variable? I would like the called service to differ whether variable is true or false.

Kindly guide :))