If there is any instance where you cannot confirm or are unsure then have the customer confirm the legitimacy of the traffic. ALWAYS ALWAYS ALWAYS change the customer facing ticket summary and details to the below client facing verbiage (You will need to add in the information) and save the ANI email as an internal log note:
Potential Fraudulent Calls – Ent Name – Date
We have received an alarm that an unusual number of international calls have been placed during the past hour from your enterprise user [List user’s name, DID , and Ext]. We will investigate this alert and take action as necessary to ensure security against fraudulent threats.