Airtel — cancellation of postpaid services are delayed and bill kept generating

Address:

Bangalore Rural, Karnataka, 561203

Airtel company does not allow cancellation of postpaid services immediately.
They will try to make all non sense communication in the name of customer retaining and bill will keep generating month on month without any usage.
They dont provide termination / cancellation of services through their portal.
They suggest cumbersome process to go for prepaid, plan change etc. By the time you realize 2 or 3 months bills are generated without any usage