добавил
xmlhttp.setRequestHeader("Content-Type", "text/xml;charset=UTF-8");
ответ стал
<?xml version='1.0' encoding='UTF-8'?>
<S:Envelope xmlns:S="http://schemas.xmlsoap.org/soap/envelope/">
<S:Body><S:Fault xmlns:ns4="http://www.w3.org/2003/05/soap-envelope"><faultcode>S:Client</faultcode>
<faultstring>Cannot find dispatch method for {http://www.sample-package.org}rety</faultstring></S:Fault></S:Body></S:Envelope>