You get these AT Calling Phone Cards at places like newsagents
They sell a variety of different ones but they all have various rates and charges
These are the best ones
You can also get a pamphlet that shows you all the cost to the different countries
It pretty cheap NZ 4.9c p/minute UK 1.7c p/minute SOUTH AFRICA 9c p/minute etc
I wouldnt get any more than a $10 one as that will last ages
They last 3 months from the first time you use them and 6 months all up
Use to ring my brother and sister in Canada and talk for an hour each week never used a $10 one up fully before it expired
Its so cheap to use
When you ring it tells you how much credit you have left and how many hours you can talk for on your card before you get put through to the person which is good