I hope this is the right place to ask.
We will be cruising to New Zealand, Australia, Indonesia and Singapore and I need some information on disposable cellphones. To begin, I have never owned a cellphone (probably the last one on the planet

, so I know almost nothing about them.
Can I purchase a disposable cellphone when I get to Auckland that will allow me to make calls while I travel. The calls could be to contact car rental agencies in the various ports, or it could even be to my kids back home if needed.
How do the charges work for these things, and what are the costs of the actual cellphones?
Many thanks for any advice!