post child contents by using current id

I’m using this code to post the child pages of the said ID but basically I want to convert this dynamically by using the_ID but when I use the_ID it posts all of the pages and posts. Doing the <?php echo the_ID(); ?> display the current ID. Not quite sure on how can I used this to control the loop.

123 is the ID of the Parent this needs to be converted to the_ID().

<?php
			$args = array(
			    'post_type' => 'page',
			    'post_status' => 'publish',
			    'posts_per_page' => -1,
			    'post_parent' => 123,
			    'orderby'=> 'menu_order',
			    'order'=> 'asc',
			);
			$query = new WP_Query($args);
			$catNull = get_template_directory_uri();
			echo '<ul class="all-service">';
			while ($query->have_posts()) {
			    $query->the_post(); ?>
				<li class="all-service-item">
					<a href="<?php the_permalink(); ?>">
					<div class="content">
						<h4><?php the_title(); ?></h4>
						<?php the_content(); ?>
					</div></a>
				</li>
			    <?php
			}
			wp_reset_postdata();?>
			</ul>