Airtel — extra bill generated

[protected] postpaid mobile registered in my name @aman kumar sharma with plan 149 per month.in the month of august 2017 i have received 10gb free data out of which used only 202.27mb and billed rs175.82 and paid on 23 sept 2017. The remaining data carried to next cycle and also received 10gb more free data out of which i have used only 2136.92 mb. But my bill for the month of september which normally should be generated on 5th or 6th of every month delayed and generated on 27th or 28th october on my airtel app as rs 783.85. My airtel app is still showing 17.50 gb data balance as on date. Till date i have not received my detailed bill through e mail which i continuously receiving every month. I talked to customer care three times and they assured me that there is discrepancy and will be rectified sòon and asked me to wait for some days. But after so many days no update is received. These days i am not using my airtel mobile due to this problem.
In the meantime the bill for month of october 2017 generated and displayed on my airtel app but after some days it is removed and bill for month of september is displaying with due date 15 nov 2017.
Kindly look into the matter thoroughly and solve my problem and inform me on my registered e mail dr. [protected]@gmail.com
So that i can use my airtel mobile with out any hesitation.
Thanks