soapCall return me xml with function's name in lowercase

Im trying to use a function called GetExample in a web service called http://ift.tt/1r1I9Y2 but when I use __soapCall function, the xml turns to lowercase. Example

$server="http://ift.tt/1r3nKAD";
$soapClient = new SoapClientDebug($server,  array('trace' => TRUE)); 

$parametros = array('Cups' => '8','Tarifa'=>'2');
$function = 'GetExample';   
$resultado = $soapClient->__soapCall($funcion, array($parametros));

And this is SoapClientDebug class:

class SoapClientDebug extends SoapClient
{
    public $sendRequest = true;


    public function __doRequest($request, $location, $action, $version, $one_way=0) {
        if ($this->sendRequest) {
            var_dump($request);
            return parent::__doRequest($request, $location, $action, $version, $one_way);
        }
        else {
            return '';
        }
    }
}   

The $request var_dump is shown like that:

<soap-env:envelope xmlns:soap-env="http://ift.tt/sVJIaE" xmlns:ns1="http://com/example/WS/OmieServices"><soap-env:body><ns1:getexample><ns1:cups>8</ns1:cups><ns1:tarifa>2</ns1:tarifa></ns1:getexample></soap-env:body></soap-env:envelope>

If the name of function is lowercase, the web service return nothing. I have seen the soapClient construct and I havent seen anything about this in http://ift.tt/1r3nKQR