Payment complete filter not working in Woocommerce

I am trying use the filter woocommerce_payment_complete_order_status. I have tried a lot of things, but I’m not able to get it to work.

function cod_to_onhold( $order_status, $order_id ) {
    //global $woocommerce;
    $order = new WC_Order($order_id);
    return 'completed';

    error_log("order marked completed", 0);

}

add_filter( 'woocommerce_payment_complete_order_status', 'cod_to_onhold', 10, 2 );