Airtel — postpaid bill - extra charges for sending international message

In my Airtel bill for Bill Period 26-Oct-2017 to 25-Nov-2017, Bill No.[protected], I have been charged Rs. 5 for sending an International Text message to[protected], whereas, I have not sent any international message to the above said number. The details as appeared in the bill are as follows:
01/Nov/2017 21:19:[protected] I want it sorted.