US iphone in Australia data plan?

I have a data plan on my iphone 5c through verizon in US right now. I plan to live in australia for 6 months and it would be extremely helpful to have data with me so I have a navigation system with the maps app on my iphone.

Question is, what is the best and cheapest way to have a phone plan i can call/text back to the US and have cellular data throughout my travels, while still using my iphone 5c. Is this possible?

1st off it would need to be unlocked in order to use any Australian carrier's service.
As far as the plan you'd have to check Australian carriers & compare their plans as far as international calls/texts to see which is best.