Airtel — undue harassment of customers and foul play

Not happy with the policies adopted by airtel stores-requested park street kolkata stores to change ownership to corporate but they converted the prepaid nos. To postpaid without our consent and now they have asked to submit the documents to convert to prepaid again and are insisting personal visit to the store to collect the simcards and are not willing to accept even the authorisation letter for collection of sims.
They take too long to resolve a problem and lots of follow up through calls and e mails is required.
Why should a person pay for postpaid if the nos. Are not used much?
The app doesn't show the excess or due amounts for landlines as it used to show in 2016 till july.
I am not happy with airtel the way they are harassing customers.
To handle property matters authorised person can handle affairs then where is airtel?