Airtel — incorrect bill charge after port out

Address:

Gurgaon, Haryana, 122001

I have port my number from airtel to idea.in the last bill, they have 500 rs extra exclude my monthly rent for internet charges (Even if i have left my 35 gb data in the account)
My number - [protected]. I go to airtel store but they said they can't raise my complaint. So please resolve my bill issue.

The company like airtel they can make such small mistakes and i can't raise the issue in the airtel store as well.