Long Duration Calls

When you receive your bill, there may be a number of Long Duration Calls highlighted which often have a high cost associated to them. How do you know who made those calls? Is it the same person making the same calls and are they business related calls? Is this usual traffic and therefore you need to investigate a cheaper tariff or is this a case of misuse or even fraud?
With Telephone Call Logging it is possible to run reports against specific dialled numbers so that you can identify which extension has made the call. You can also run reports using wildcards so that you can identify all calls that, say, were dialled that included the last four digits, etc.