Airtel — Airtel deleted my prepaid number without any prior notice

Airtel deleted my prepaid phone number all of a sudden without any prior notification. Upon going to the store, they are not guaranteeing that my old number will get reactivated. I have also reached out to airtel nodal officer and not getting any resolution. Please help me with a resolution. I really need my original number back and I have been using this for 15 years and it will be a bigger problem to change contact number.