ExternalReportWSSService -> runReport failing with error 415 Unsupported Media Type

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I am trying to run a simple report from pl/sql using ExternalReportWSSService -> runReport and it is failing with error 415 Unsupported Media Type. The same payload works from SOAPUI. Below is the payload. Any help is appreciated.

I have set the headers as below -

apex_web_service.g_request_headers.delete();
        apex_web_service.g_request_headers(1).name := 'Content-Type';
        apex_web_service.g_request_headers(1).value := 'application/soap+xml;charset=UTF-8';
        apex_web_service.g_request_headers(2).name := 'Content-Language';
        apex_web_service.g_request_headers(2).value := 'en';
 

Rest of details are in the attached document.