Look at...

WHAT IS VOIP

On google.com

VOIP can be a do it yourself project, but I will not hold your hand to make your own VOIP system. I will help you find the right words to put into google.com

I helped someone make a "gateway" from phone to internet by running a phone/voice card and specialized software (sorry, they write such and you can't ask me for it or its name) and the end effect was that you call this number and then you can use a voice chat over the internet application.

Hope this helps you get your project started.

In closing, if you type in all capitals again, I will not respond.

Bob