This service is ready to pay 

You need to connect an additional payment system
http://www.redsys.es/wps/portal/redsys/publica/areadeserviciosweb/descargaDeDocumentacionYEjecutables/
to the existing site is written in WEBSITE X5 - Prof. Specifically basket x5cart.js. Usually very easy to connect the new payment system is enough to have the HTML code. In the code, you will need to add a variable [price] so the program fills it with the price to pay and [ORDER_NO], to add your order number in the payment, so that you can identify it.
Merchant company unfortunately has not yet provided HTML CODE. Therefore, we need experts who can deal with the php code for WooCommerce and translate it into a simple html or html + php.
It is necessary that it can be added to the program WEBSITE X5 - Prof and further easily update without using handmade in the future.