Ethernet Shield

Hi there.

I'm new to arduino and have not done much programming in a few years.
My goal is to use the ethernet shield to connect to a specific VoIP phone over a quite large telephone and send some type of message, either text or audio.
Can anybody inform me if that's possible and how I must approach that kind of project?
Should I connect the arduino as a client to the main phone server, connect it to a phone that is already part of the network, use it as a server to one of the phones, etc?

Thank you in advance

How would you perform the same task using a PC?

Once you know how to do that, making the Arduino with Ethernet shield do the same thing will either be obvious, or it will be obviously impossible.