Airtel — airtel wrong postpaid bill

Address:

411028

Hi,
In my postpaid bill, there is a wrong entry of isd call.
When i called support no first time, support rep checked my mob no details and confirmed that isd is not even activated on my no. She asked to wait for her next call about the same, however i did not receive any call from her.
After 2 days when i called support no, i have been told that for each number isd gets automatically activated. This is pathetic. I never called any isd number nor i activated it on my number, but still that call entry is added in my bill.
Now that support person is saying, i have to pay the bill as that entry is coming and they cannot help me in this.
Very bad experience of airtel.