Airtel — 4g sim showing 3g

On 18/03/2020 i had recharged my mobile no. With rs.399/-. According to that pack i am suppose to get 4g speed. Which i am not getting. While i approached the airtel outlet at bunts hostel, mangaluru on 19/03/2020 and explained my problem to the concerned staff. After checking my mobile and shifting my sim to her mobile and all checking is over, she came to the conclusion that 4g facility is suspended to my sim without giving specific reasons for the problem. Upon that, she informed me that me sim is not registered in my name. I am wondering how can this happen. I am using this sim since 13 years and myself i have purchased this sim from airtel outlet at pandeshwar. I had submitted my aadhaar copy and my pan copy at the time of purchasing my sim. At the time of activation they have verified my address my aadhaar number. I have completed all procedure like updating of my sim to 4g network, linking my mobile number to my aadhaar no. I am still puzzled. How can my sim suspend the 4g facility on 18.03.2020, when it was working till 17.03.2020 11:00 p. M.