How will this be used?
PinSet Pro is a good solution if you are mostly tracking people time, e.g. to ensure that an attorney’s hours are billed to the correct client. Or, if the same physical phone is used by staff from different departments, or a extension user makes calls on behalf of different departments.
Otherwise, could you just have a table e.g. in Excel that maps extension numbers to departments and processes the CDR’s accordingly? This would save all users the trouble of remembering and entering PINs.
Also, most calls are not literally dialed – they are placed from corporate directories, phone contact lists, CRM systems, phone history, speed dial buttons, redial key, etc. Depending on your devices and systems, adding a PIN may break some of these methods or require manually entering the PIN after ‘automatically’ placing the call.
In most developed countries, quality trunking service is under one cent per minute, likely less than 1% of the cost of the person making the call. Don’t let the bean counters cut into productivity.