def call(self, addr, data, namespace, soapaction = None, encoding = None,
    http_proxy = None, config = Config):

    if not isinstance(addr, SOAPAddress):
      addr = SOAPAddress(addr, config)

    cookie_cutter = ClientCookie.HTTPCookieProcessor(config.cookieJar)
    hh = ClientCookie.HTTPHandler()

    opener = ClientCookie.build_opener(cookie_cutter, hh)

    t = 'text/xml';
    if encoding != None:
      t += '; charset="%s"' % encoding
    opener.addheaders = [("Content-Type", t),
              ("Cookie", "Username=foobar"), # ClientCookie should handle
              ("SOAPAction" , "%s" % (soapaction))]

    response = opener.open(addr.proto + "://" + addr.host + addr.path, data)
    data = response.read()

    # get the new namespace
    if namespace is None:
      new_ns = None
    else:
      new_ns = self.getNS(namespace, data)

    # return response payload
    return data, new_ns