How to move a post from one category to another

add_action('wpcf7_mail_sent', function ($cf7) {
    $submission = WPCF7_Submission::get_instance();
    $data = $submission->get_posted_data();

    if( empty($data['_wpcf7_container_post']) )
        return;

    $post_id = (int) $data['_wpcf7_container_post'];

    wp_remove_object_terms( $post_id, 'available', 'category');
    wp_set_object_terms( $post_id, 'booked', 'category');
});