How to redirect to thank you page after woocommerce checkout order processed

im trying to change order status to “completed” and skip payment page (go to thank you page) after order is processed.

so far i manage to change order status to completed but instead of redirecting me to thank you page, i will be redirected to payment page with the following error :

this is the code i use :

add_filter( 'woocommerce_checkout_order_processed' , 'skip_join_payment' );
function skip_join_payment( $order_id ) {
     if ( ! $order_id ) {
        return;
    }
    if( $_COOKIE['isjoinForFree'] == "yes" ){
        $order = wc_get_order( $order_id );
        $order->update_status( 'completed' );

        ** i tried to redirect here but getting error on checkout page **
        // if ( $order->has_status( 'completed' ) ) {
                // header("Location: /jtnx/");
                // die();
        // } 


    }
}

in addition i tried adding another hooks with redirect :

add_action( 'woocommerce_payment_complete', 'skiped_join_payment_redirect', 1 ); 
function skiped_join_payment_redirect ( $order_id ){
    $order = wc_get_order( $order_id );
    if( $_COOKIE['isjoinForFree'] == "yes" ){
    $order = wc_get_order( $order_id );
    if ( $order->has_status( 'completed' ) ) {
            header("Location: /jtnx/");
            die();
        } 
    }
}