magento_soap_v2_catalog_product_type_configurable_assign.php

<?php
$client->catalogProductTypeConfigurableAssign($session, $configurableProductIdOrSku, $simpleProductIdsOrSkus,
    array('color','size'),
    array(array(
        'key'=>'color',
        'value'=>'Color'
    ),array(
        'key'=>'size',
        'value'=>'Size'
    )),
    array(
        array(
            'key' => 'yellow',
            'value' => array(
                'pricing_value' => 35,
                'is_percent' =>0
            ),
        ),
        array(
            'key' => 'XL',
            'value' => array(
                'pricing_value' => 20,
                'is_percent' => 1
            )
        )
    )
);