Airtel — Wrong Broadband Billing

This is about the Airtel Broadband connection. I have taken Advanced Rental Plan for a period of 1year starting from 01-Jul-21 to 30-Jun-22. Plan rental was Rs. 999/month. Now, from June Month Airtel started calling saying Bill payment amount of Rs1178/- is due for 17 May -16June period. There were mails regarding it and apps also started showing Amount due for payment and warnings on connection will be disconnected. Later in June, the connection got disconnected. After continuous try with customer care, I was told by the airtel executive that problem is fixed and there is no amount to be paid. But, now in August, I am getting the mails and calls saying to pay Rs2593.64. This is purely harassing the customer.