Airtel — Sim card used by my father is issued on someone else name

Dear Sir/Madam,

This is regarding my father's Airtel SIM card which he has been using for the last 9+ years, recently his sim card stopped working and when we went to the Airtel store I was told that the number is registered on some one else name which is strange to say the least. We do remember is like any other responsible citizen, mobile phone user in India, we had submitted my father's identity document when we purchased the SIM card and since its been quite sometime since he is using the sim card, we would like the number to remain with him. Can you please please help us in this matter?? We can resubmit my father's identity documents once again if need be to keep the same number. Details of Airtel Number Father's name - Sunil Kumar Das
Number - [protected]

Please reach me out on [protected] if you have any questions.