Airtel — wrongly charged for rental service for august month despite being on safe custody

My airtel broadband account/services were deactivated and on safe custody from mid july and i paid the combo pack which is 500 + tax for 3 months. I reactivated the services in august end and the company is charging me for the month of august even though i paid for the combo pack. I have the emails from airtel stating that my safe custody was activated and i have been trying to follow up withe company but every time i call them they say and admit that there was technical issue but they do not resolve it and say supervisor will call but no one calls and it's been almost a month but they haven't resolved it. Also now they have stopped the broadband services due to non payment of bill which they have charged incorrectly.
Airtel fixedline number: [protected]