Airtel — Fraudulent ISD charges when no ISD calls done

Airtel has charged ISD calls in my mobile bill in Jan 2023 of around Rs 1555 + taxes.
No ISD calls were made. After reaching out to customer service they asked me to pay the bill while they investigate. Customer service mentioned that the additional payment will be adjusted in next month. At the same time on 28 Jan 2023, I had told to deactivate the ISD services linked for my numbers. This month again I was charged Rs 1348 + taxes ISD charges in my mobile bill even after deactivating ISD services. Complaint IDs with Airtel are[protected] raised on 28 Jan 2023 and[protected] on 28 Feb 2023.
Airtel is claiming that the calls are valid and not fraudulent.
They are also not sharing the details of the ISD calls. Why should I pay for fraudulent calls when I have deactivated ISD services. I am not getting satisfactory response from Airtel .Neither a waiver on the charges for the calls I have not made