Yes sir all you have to do is use your regular Internet connection and talk to Uncle Ned across the pond for free. The only problem is that packet-switching used in the Internet is that data signals consists of short burst. Which means that lot of users can share a small amount of transmission bandwidth. Each users data is broken into many short packets, which are then routed then routed separately over different paths to the final destination where the entire message is reassembled, frequently with some delay. This delay prevents the simultaneity of a two-way telephone conversation.
Voice calls tend to be long in duration and require a continuous connection with no delay.
That is where the rub comes in. I don't want to belabor the point here, or talk about the various compression techniques used by the Telephony wizards. Indeed, at some point in time Internet IP Telephony will probably work, and work well, but for now let's just put it back on the shelf.