Airtel — airtel postpaid cancel my postpaid number -[protected]

Airtel postpaid — cancel my postpaid number -[protected]
Dear sir/ madam,

I would like to surrender my postpaid sim card number [protected].

Kindly cancel my number.

My sim was broken back in may 2018 and not in usable state.
I went to near by airtel showroom to requesting to cancel the number since travelling to abroad and no longer needed. They asked me to send an email to [protected]@in. Airtel.com to cancel the number and i did the same on june 18, 2018 but still the number has not cancelled and getting monthly bills with fine. Tried to reach customer care at 121 but they are asking to enter account number but there is no account number in airtel bill. Very frustrating, still number is not cancelled.

I am authorizing to cancel my number immediately.

Please help.