Idea Cellular — Idea sim/ complaint regarding my id proof over the sim has been changed

Respected sir, I have purchased an idea sim 5 years ago and had been using it regularly. It has been broken 10 days ago and I thought of getting a new sim on the same number. But as to my surprise, the sim is registered on on another id proof whose i dont even know. How is this even possible. Now how can i get the same number as it is very important to me.