Airtel — my phone number allotted to someone else

Address: New Delhi, Delhi, 110016

Website: Airtel.in

I have been using my mobile number [protected] for past 11 years...In august 2017, I had changed my handset so got new sim & wasn't using it...In December 2017 i inserted the sim again in other handset, it showed inactive...visited airtel store, submitted my Adhar number, & wAs given new sim, with assurance that it will b active within 2 days with same number...

But even after 2 weeks it didn't activated & recently came to know my number is allocated to some one else.

How can my number be allocated to some one else?

This number is update in all my bank accounts, demat, pan detail, aadhaar account. ...Paytm accounts...my Exam updates also come on same number...

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.
Even currently I am Airtel user, but i did not expect airtel to act so irresponsible which put mt at very high risk.

Kindly take this matter urgently and give me chance to re activate my number.

Thanks & Regards
Purnima