Airtel - Airtel postpaid

Hi , I am been harrassed n double charged by Airtel every month and every month I need to call them to hv the issue fixed. Since November ****, I have been charged double my bill n sometimes even more than that on my bill. My bill plan is Rs*** for two numbers and with tax, it should not be more than Rs***. However, they charge me anything between Rs**** to Rs**** plus every month. There is a bug issue in there system and they reverse the duplicate monthly bill for Rs*** which they charge in error, however there is no reversal for the taxes that they charge extra. This month they charged me Rs****.** and when I called to speak to them, there was no one to take care of the issue. I messaged them on Fb and they only reversed Rs*** as gud will. When I kept send them messages then they reversed the late fee of Rs ***, however they need to reverse more money as my bill shud be only Rs***. When I ask them to call me, they give me one ring miscall and send me a message saying we tried calling u but I was unavailable. I dont know who do I contact as in this lockdown it seems that there service centres do not have reps available. The company is horrible to deal with.