function maybe_cancel_subs( $user_id, $user_tags ) {

    $subscriptions = wcs_get_users_subscriptions( $user_id );

    foreach ( $subscriptions as $subscription ) {

        $product_ids = array();

        foreach ( $subscription->get_items() as $item ) {

            $product_ids[] = $item->get_product_id();

        }

        if ( in_array( 123, $product_ids ) && $subscription->get_status() == 'active' && wp_fusion()->user->has_tag( 'Cancel 123', $user_id ) ) {

            $last_order = $subscription->get_last_order();
            WC_Subscriptions_Manager::cancel_subscriptions_for_order( $last_order );

        }

        if ( in_array( 456, $product_ids ) && $subscription->get_status() == 'active' && wp_fusion()->user->has_tag( 'Cancel 456', $user_id ) ) {

            $last_order = $subscription->get_last_order();
            WC_Subscriptions_Manager::cancel_subscriptions_for_order( $last_order );

        }

    }

}

add_action( 'wpf_tags_modified', 'maybe_cancel_subs', 10, 2 );