Airtel — Airtel postpaid charging illegal

Hi,
I am in Airtel Black Plan, One of my postpaid mobile AIRTEL has charged on my post Paid bill around 324 rupees for using the services of 543212(which
we haven't used this service. i wonder by seeing this bill and called the AIRTEL customer care service people. There way of answer is very rude and disrespecting the customer. They are not ready to investigate on why this bill was charged and also not ready to show the proof .
I feel very bad that this people are charging illegally and making our money and time waste .I need justice for the above and want to clear whose fault is this..

Thanks
Christopher - [protected]