No operation available for request error in SOAP UI

Hi Experts,

From SOAP UI we are passing SESSION ID PO# and Item # to Sales Force. Please see below code

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:draw="http://soap.sforce.com/schemas/class/Draw_Downs_WS">

   <soapenv:Header>

      <draw:AllowFieldTruncationHeader>

         <draw:allowFieldTruncation>?</draw:allowFieldTruncation>

      </draw:AllowFieldTruncationHeader>

      <draw:DebuggingHeader>

         <!--Zero or more repetitions:-->

         <draw:categories>

            <draw:category>?</draw:category>

            <draw:level>?</draw:level>

         </draw:categories>

         <draw:debugLevel>?</draw:debugLevel>

      </draw:DebuggingHeader>

      <draw:CallOptions>

         <draw:client></draw:client>

      </draw:CallOptions>

      <draw:SessionHeader>

         <draw:sessionId>00De0000005NAQx!AQwAQJaZ6un5nVJk.EnVZ_rLiV4rEseAkdNwrJNqGDyzZutAmwe_tbXPsh7rzNORFRup1roEvL5PFIFBb.m9wlSfPmpDHq0n

</draw:sessionId>

      </draw:SessionHeader>

   </soapenv:Header>

   <soapenv:Body>

      <draw:getInvoicesRecords>

         <!--Zero or more repetitions:-->

         <draw:qValues>

            <!--Optional:-->

            <draw:ItemNumber>1</draw:ItemNumber>

            <!--Optional:-->

            <draw:SrmPO>431000315</draw:SrmPO>

         </draw:qValues>

      </draw:getInvoicesRecords>

   </soapenv:Body>

</soapenv:Envelope>

But we are getting the response as below mentioned

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">

   <soapenv:Body>

      <soapenv:Fault>

         <faultcode>soapenv:Client</faultcode>

        <faultstring>No operation available for request {http://soap.sforce.com/schemas/class/Draw_Downs_WS}getInvoicesRecords</faultstring>

      </soapenv:Fault>

   </soapenv:Body>

</soapenv:Envelope>

Please suggest if any ideas to rectify this.

Regards,

Rafi