Airtel — Airtel refuses to cancel mobile number

I recently got a postpaid number [protected]. Once it got activated, I started getting a lot of calls from unknown people wanting to speak to some Sonawale. I kept saying wrong number and blocking the calls. Still I got calls from new numbers on daily basis. I send email to Airtel ([protected]@in.airtel.com) to cancel my number and also requested a refund of the initial amount for the same. They completely ignored that and did not respond. I tried sending email again next day and the day after and still no response. Then I messaged them via Twitter to see if they will respond there and they asked me to block the numbers and then asked me to put DND. I explained that these are not telemarketers but people who want to connect with the previous owner of the SIM and they continued to keep saying block numbers and DND and the conversation was just looping over like as if talking to a dumb machine. I eventually told them at this point I'm frustrated enough with their service that I'd cut my losses short and just asked them to cancel my number and they can keep my money. And they reply with the same DND and blocking number message. They absolutely refuse to cancel my number despite multiple requests. What can I do to make these brain dead people take action?