Making phone calls in Chile

It is the same process as most other countries. Once you rent a place, contact the phone company to install a land line. Entel is one of the bigger cell phone companies down there. Stores everywhere.

I actually have an american IP based phone system. So I just bring my phone down, plug into the network and it is like I am in America.

Yes, i agree with Eric. We brought a magic jack which is VOIP. Plug into your computer with internet service and you are talking!
We can call the USA and friends can call us like we were still in the USA.
Once you get residency, you can get a landline or cell phone plan. You must show them a proof of income or even that you just have money in the bank. Movistar, a cell phone co. here, just wanted an ATM receipt showing our balance.
We do not have a plan on our cell phone but just pay for minutes as we go. It may be slightly more per minute but we can get away with just paying $20 or less per month. The problem with this is though you may run out of minutes while in the middle of a call! But you can still receive calls.
Another consideration is that if you don't use all your minutes by the end of the month, you lose them!