Originally posted by: tony4704
thanks for all the info guys, appreciate it. This was just what I was looking for.
So if I were to call home from my cell would that not cost anything additional to either myself or the person I am calling?
I'm not sure that I understand the question. If you call anyone in the US, they won't pay anything no matter what (unless you call their cell, in which case they'll use minutes or prepaid minuteS).
If you call the US from NZ on an AT&T SIM with your normal iPhone, you will magically appear to US callers as your local US number, but will be charged for an international roaming cell phone call. I don't know what this costs, but think $4/min. as a general starting point and you'll be close. There's a $5/month plan you can get that takes this down to a less-jaw-dropping ~$2/min. call, but this is still a lot.
If you unlock your iPhones and use Vodafone SIMS and call the US on the Vodafone SIM on your unlocked iPhones, you will appear to US callers to be calling from NZ and you will be charged for an international NZ->US call. Again, no idea what this will cost, but use $1.50/min as a guess.
Alternatively, you can download Skype and then call from your iPhone when you are near a WiFi point (they are less prevalent there than in the US, but still easy enough to find). This will cost pennies per minute. I did this when I was in Europe this summer and it worked great. Practically free international cell phone calls are a neat thing.
Alternatively, you unlock your phone, buy a Vodafone SIM, and then can buy a calling card for NZ for international calls and then call the 0-800 number or whatever their free calling number is (I think it's 0800), and then enter the code, and then the US number, and then you'll pay very little for the call (I believe 800 calls in NZ on a cell are free and don't use minutes but I haven't been there in years and can't remember.)
The one thing that you definitely do not want to do is to go to NZ with an AT&T SIM in your iPhones and then do a lot if Internet stuff. This will cost you a small fortune. The iPhone helpfully will access the internet itself a lot - even when it seems like it's in standby or when you aren't doing anything on the internet at all. So if you decide on the non-unlock route, definitely make sure you turn "data roaming" to off in the Settings -> General -> Network menu.