Webmethod MTOM Queries

I followed official docments to prepare a MTOM demo. This demo works fine, but not what I expected. What I want is that make a MTOM attachment case. Attach files into MTOM attachment instead of SOAP message body like:

<?xml version='1.0' encoding='utf-8'?>

<soapenv:Envelope xmlns:soapenv=“http://schemas.xmlsoap.org/soap/envelope/”>
<soapenv:Header />
<ns1:receiveAttachmentAndSFTPout xmlns:ns1=“http://AARON-THINK/MtomDemo.ws:receiveAttachmentAndSFTPoutWS”>

How could I attach files into MTOM attachment instead of message body?
MTOM Demo.docx (690 KB)