Pasted

<?php
 /**
 * Translate Text using gettext filter/hook
 * As for where to paste this : http://wp-events-plugin.com/tutorials/how-to-safely-add-php-code-to-wordpress/
 */
function change_text( $translated_text, $text, $domain ) {
        switch ( $translated_text ) {
            case 'Thank you for your payment. Your transaction has been completed an you will soon receive an email confirmation.' :
                $translated_text = 'Gracias por tu pago. Su transacción se ha completado y pronto recibirá una confirmación por correo electrónico.;
                break;
         }
    return $translated_text;
}
add_filter( 'gettext', 'change_text', 100, 3 );