Airtel — My number has been deactivated without any reason.

I have been using this number since last 2 years. Now it's been 15 days the number is deactivated. Every time I contacted the customer service I was told that the number is not an Airtel number. Nothing is there in their records. When contacted the airtel store I was told to provide them a stamp. Even then they say they are not sure if the number will get activated. I am a working woman in government service. This is my official number. I am stuck. I don't know what to do.

This is my number [protected]

Please help.