HTTP Advanced sensor's display Unsupported Media Type

Hello All, I'm trying to monitor a Webservices server using the HTTP Advanced sensor. In order to test my request I used SOAP UI, and from this tool I'm getting a correct server response. Then I copy/paste the same query into the POST DATA setting of the HTTP Advanced Sensor From the time being, i'm always getting an output: HTTP/1.1 415 Unsupported Media Type

In the URL field I set this value : https://mywebsite.com/WSV2/MerchantService?wsdl

Then in Post Data :

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xls="http://xxxx.com/schema/xls-model-mc-svc" xmlns:xls1="http://xxxx.com/schema/xls-model-core">
   <soapenv:Header/>
   <soapenv:Body>
      <xls:CampaignRewardReq>
         <!--Optional:-->
         <xls1:Credentials>
            <xls1:Username>xxxxxx</xls1:Username>
            <xls1:Password>xxxxxx</xls1:Password>
            <xls1:Realm>xls</xls1:Realm>
         </xls1:Credentials>
         <xls:CampaignID>32</xls:CampaignID>
      </xls:CampaignRewardReq>
   </soapenv:Body>
</soapenv:Envelope>

In Custom Content Type : application/soap+xml

Do you have any clue about this problem?

Thanks a lot in advance! Cheers, Cédric