SOAP Receiver: Problem with SOAP Multipart Request (wsdl:part)

Dear PI experts,

our partner provided a WSDL with the following definition (I modified it to keep it simple and showing the principles)

<wsdl:message name="nameOfMessage">

<wsdl:part element="part1" name="header" />

<wsdl:part element="part2" name="parameters" />

<wsdl:part element="part3" name="attachment" />

</wsdl:message>

After importing this WSDL in ESR, I found the following definition on tab 'WSDL':

<xsd:complexType name="nameOfMessage">

<xsd:sequence>

<xsd:element name="header" type="authentication" />

<xsd:element name="parameters" type="businessDatal" />

<xsd:element name="attachment" type="Binary" />

</xsd:sequence>

</xsd:complexType>

When creating the request message in PI it looks as follows:

<nameOfMessage>

<header/>

<parameters/>

<attachment/>

</nameOfMessage>

However our WebService provider expects the following:

<soap:env>

<authentication/>

<parameters/>

<attachment/>

</soap:env>

When using SoapUI and importing the WSDL the request message looks as expected by the web service provider and the part names are resolved.

I could try to convert the request using XSLT but this does not seem to be a best practice approach.

Do you have any advice on how to handle this issue?

Thank you very much.