1). Find the BW service server process which contains the "SOAPSendReply" activity. In the process definition "Configuration" table, click "Namespace Registry" and add "http://schemas.xmlsoap.org/soap/envelope/" (the last "/" after "envelope" is required) and prefix "soapenv".
2). Click "SOAPSendReply" activity. Switch to "Input" tab. On the right "Activity Input", click the root element "SOAPSendReply". Click "!" above which means "edit statement". You will see the statement type "template". Check "exclude result prefixs". Do not enter any prefix name.
3). Do a TCP trace. The reply will resemble "<soapenv:Envelope...<soapenv:Header...<soapenv:Body..." although the cliecnt request is "<SOAP-ENV:Envelope..." .
See the attached for reference (Filename: soap_headers_replace_ns_prefix.zip).