Calls that hang up immediately after answering often signal scam attempts or automated robocalls testing active numbers. In this case, the silent drop from a New Zealand line to Australia fits patterns of international spam, where scammers probe for responses to avoid wasting time on dead lines. Don't call back, as it could confirm your number is live and lead to more harassment. Block the number right away and report it to your carrier or authorities like the ACCC in Australia. If it persists, consider apps that screen unknown callers to cut down on these nuisances.
The call was placed to Australia, but the line was disconnected immediately after I answered.