Hi Sriharsha

As per everyone else's comments, this one sounds like a potential nightmare.

The managers will undoubtedly also want some kind of log to show which employees dialled an outside number and when, perhaps also how long the call was. This would need a real-time clock source, plus some kind of storage for the data, plus a mechanism by which the data can be read out and viewed.

I think you would be working on this for a very long time, the cost would be very high!