Generating SOAP Envelope when DO NOT USE ENVELOPE option is marked

My scenario: SPROXY => XI => 3rdParty WebService. Communication is synchronous. I've a problem with soap envelope. It is required by webservice, but when I use standard soap envelope generated by SAP I've a problem with receiving response from webservice.

So I want to create my own envelope. For this reason I've used DO NOT USE SOAP ENVELOPE option. Now the challenge comes. How can I create my own soap envelope?

Do you have any working example? Soap envelope should be added to message send from XI to 3rdParty WebService.

Helping answers => a lot of points 😊