Airtel — assignment of my phone number to others

Address:

Bangalore, Karnataka, 560056

I am using the number [protected] since past 8 years and now since i had to be abroad for some time and i had no good reception there, i did not use it for 4 months and now when i tried to reactivate it, the customer care said that my number has been reassigned to someone else. It's unfair to treat a customer this way regardless of what the rules say. I want my number back since i have linked all my banking accounts to it. Strangely enough, there was not a single call from the customer care or any warnings via texts. Please help