(Help) land line -> server -> iPhone (I am complete novice)

alright i am a complete novice and need a little hand holding here, and i am not a shamed of saying that. Any way i run a small I have a business and I have an iPhone, and a laptop. I want to be able to connect my land line to a server then from the server to my business network. and connect to it from a VoIP app. I also want my analogue network to work as well so i can answer the business phone on my iphone, I the last thing want to be able to do is pick up and listen while some one else is on the line.

Info i need:
Is this possible?
I have a server, what parts do i need?
can I use all these feature in a Starbucks or on 3G

Basically I want to integrate my iphone and my land line

Thank you so much for helping me i really appreciate it!

p.s. I would never actually use it in a Starbucks, too insecure I am not a dumb ass :stuck_out_tongue:

so i watched a video on system about asterisk and it realy helped. so i am done here.