Airtel - post paid amount more than used

This is Ashwini from Mumbai. I was using airtel postpaid connection, last month I ported to vodaphone.in every month bill they are adding extra amount.
They are working like a fraud.
Customer care executive is also talking in a rude way.
I have taken a plan of *** and in each month they are sending a bill of around ***.
This month they send a bill of **** because I ported to vodaphone.
Please look into this issue seriously, alot of customers are affecting because of there fraud behaviour.
I have seen so many complainta on Airtel website which was not responded.
That's why I am writing my complain here.
Thanks