Multiple values in WP_Query : category__and

I’m little unclear from your question if the criteria has to match the Product AND the Service .. or the Product OR the Service. You can change the ‘relation’ parameter to achieve this (AND or OR)

$args = array(
    'posts_per_page'  => -1,
    'cat' => 7,
    'meta_query' => array(
        'relation' => 'AND',
        array(
            'key'     => 'product_customfield',
            'value'   => 2,
            'compare' => '=',
        ),
        array(
            'key'     => 'service_customfield',
            'value'   => 5,
            'compare' => '=',
        ),
    ),
);
$query = new WP_Query( $args );