Airtel — my number [protected]

Address:

600010

We have been using the above mentioned airtel number for more than 15 years and this number is disconnected because of no usage (First time in 15 years).
After we come to know about it, we have been in touch with airtel through the email, no action has been taken and no options provided to me to get the number back.
I am in a short assignment period working in united states and no provision given to contact airtel except through email and their only response to go and contact airtel store which is not possible for me as i am out of the country now.
While this outstanding complaint is on with them, now it looks to be like this number is given to somebody else and all my personal financial transactions are going to that number which provides further issues as all my information is now shared to the third party.