How to set single schedule event in wordpress after some action performed

I have a function which sends an email when a task is completed

   function complete_task($id)
   {
      wp_mail('abc@mail.com','test subject', 'test message');
   }

Now I want to change this as when a specific task with the ID is completed then it should not send an email instead of registring a schedule event. I have done this with wp_schedule_single_event

my code for this is below:

   function complete_task($id)
   {
      if($id!=3) // 3 is any ID
       {
            wp_mail('abc@mail.com','test subject', 'test message');
       }
       else
       {
           add_action( 'send_single_email_event', 'do_this_in_after_1_hour', 10, 3 );
       }
   }

I have added the add_action hook in else section because in codex there is written to add this in a function you can check it here
Schedule an event one hour from now

   // function for sending schedule event
   function do_this_in_after_1_hour() 
   {
     wp_mail( 'abc@mail.com', 'test subject', 'test message');
   }
   // singdle schedule event
   wp_schedule_single_event(time() + 3600, 'send_single_email_event');

its not working, mean not sending email.