Airtel — [4g hotspot device: [protected]] how to get my airtel connection terminated.

Address: Bangalore, Karnataka

After a huge disappointment from the so called self-claiming fastest network in india, airtel, i have finally decided to get my connection terminated.
I have been trying to terminate my airtel connection via mails since last one week, but did not receive any reply from airtel.
I visited airtel customer care centre, but there also i was returned and asked to send a mail which i have already tried. I have tried sending reminders too.

Can some one help to get rid from airtel?
Also i don't want to pay rental from the day i asked them to terminate my connection.
Can i lodge an fir against airtel for cheating customers?