Airtel — my airtel number allotted to someone else

My airtel number alloted to someone else
I have been using my mobile number for past more than 5 years. When i inserted the sim it showed roaming but I am not receiving any messages or OTP.This number is update in all my bank accounts, demat, pan detail, aadhaar account. My privacy is at risk as all the sms (Verification code, otp, urn) still goes to this number and i am fully prone to fraud as well because of exposed information. After this long service i did not expect airtel to act so irresponsible which put me at very high risk. Kindly take this matter urgently and solve the issue