Airtel — Bill send for postpaid but sim not provide

Sir i am airtel prepaid user I have seen airtel advertisement regarding it's postpaid plan. I am checking plans also ask my mobile number to send otp for verification just like all other online service providers like bank bazaar police bazaar n many other service provider do for lead generation.
Ok I have seen plans there as usual there is information that u will get sim at door step .
I think may be thay will do formality n all security deposit, verification of resident etc .
Ok after that I left that web page and also no one content me even in telephone. Suddenly on August 1st week I got sms from airtel that ur postpaid bill rs 1106 is due. I get confused as I'm prepaid user and also recharge for annual pack n I called to customer care and it's surprising for me that my no us converted to post paid n also my old pack is laps.
I have enquired future thay told me that u enter otp so it's ur fault.
I tell them I have not given concern for this no and also reversed my no to prepaid also pack is full for 1 yr thay told me sorry we can't do it untill u will not repay all duse. And also ur old pack will also laps
I ask him u didn't ask for paper, security . U didn't provide me my new SIM card how u charge for it thay didn't reply me satisfactory n even not agree to register my complain. Last 3 days I'm sending messages to them thay didn't do anything and last day of payment is also coming after thay will impose penalty also.

Shailesh shukla