Beginner Question - URL Encoding

Hi,

I am working with what is supposed to be a simple SMS service. My provider haas provided me with an endpoint, I plugged it into SOAP UI and all looked good. However when I submit the message I was not getting the expected response. On dealing with the providers support team they informed me that my payload was not reaching them in a URL-Encoded format and that I need to fix this. Here is an example of the message I send and and a seperate example of what they want to receive. Any help would be hugely appreciated:

<soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope" xmlns:app="http://**************************">
<soap:Header/>
<soap:Body>
<app:upload>
<!--Optional:-->
<app:xmlString>
<gviSmsMessage>
<affiliateCode>***********</affiliateCode>
<authenticationCode>**********</authenticationCode>
<submitDateTime>2011-09-26T15:11:00</submitDateTime>
<messageType>text</messageType>
<recipientList>
<message>This is a test message to one recipient</message>
<recipient>
<msisdn>0825753495</msisdn>
<customData>
<inputCode>34567</inputCode>
<decision>AA</decision>
</customData>
</recipient>
</recipientList>
</gviSmsMessage>
</app:xmlString>
</app:upload>
</soap:Body>
</soap:Envelope>


XML=%3C%3Fxml+version%3D%221.0%22+encoding%3D%22UTF-8%22%3F%3E%0D%0A%3CgviSmsMessage%3E%0D%0A++++%3CaffiliateCode%3EZZZ022%3C%2FaffiliateCode%3E%0D%0A++++%3CauthenticationCode%3Eapplink%3C%2FauthenticationCode%3E%0D%0A++++%3CsubmitDateTime%3Eyyyy-MM-ddTHH%3Amm%3Ass%3C%2FsubmitDateTime%3E%0D%0A++++%3CmessageType%3Etext%3C%2FmessageType%3E%0D%0A++++%3CrecipientList%3E%0D%0A++++++++%3Cmessage%3EThis+is+test+message+to+one+recipient%3C%2Fmessage%3E%0D%0A++++++++%3Crecipient%3E%0D%0A++++++++++++%3Cmsisdn%3E0722141029%3C%2Fmsisdn%3E%0D%0A++++++++%3C%2Frecipient%3E%0D%0A++++%3C%2FrecipientList%3E%0D%0A%3C%2FgviSmsMessage%3E