lekiend on "[Plugin: WooCommerce - excelling eCommerce] Gateway Callback issue"

Hello,
I'm creating a new gateway.
It works like a charm but i can not get the response from the payement company.
They send an XML string by HTTP on the WC callback url.
I can not the $_POST['XML'] on an url like
http://www.mywebsite.com/?wc-api=WC_Gateway_myGateway

$_POST returns wc-api=WC_Gateway_myGateway and not XML.

Any idea how to fix that ?
Thanks
Dimitri

http://wordpress.org/extend/plugins/woocommerce/