Mr. X is a newly promoted employee who is very particular with his new found status. He would tell his former colleagues who are now his subordinates to call him Sir because according to him to be called Sir is like music to his ears and besides it tells a lot of his status in their office.
Your promotion must not go to your head because instead of building bridges you start to build walls. As you ascend higher in the organizational hierarchy It’s better if you bring yourself closer to your subordinates. Thus, you build teamwork and you enhance office solidarity.