Delete post meta conditionally after save post

I want to update/delete a post meta when a custom post (in this case custom post type is “booking”) is updated upon the change of post meta . In my case if user change the post meta booking_status to ‘denied’ and then update the post, then I want to delete the post_meta booking_status immediately .

Here is what I have tried

add_action( 'save_post', 'booking_status_is_updated' );

function booking_status_is_updated(){
   global $post;
   if($post->post_type =='booking'){

     if(get_post_meta($post->ID,'booking_status',true)=='denied'){
         delete_post_meta($post->ID,'booking_slot');
     }

   }
}

But this is not working ? How can I get it done ?

• Well, first use the hook properly. The post ID will be passed in. You
  don’t need $post->ID.
• Second, use the correct hook. If you want to run save_post only for
  your booking type, use save_post_booking

But otherwise, the code works. I just ran a quick test.

function booking_status_is_updated($post_id){
  if(get_post_meta($post_id,'booking_status',true)=='denied'){
    delete_post_meta($post_id,'booking_slot');
  }
}
add_action('save_post_booking','booking_status_is_updated');