Calls that ring briefly without leaving a voicemail often signal something shady, like automated spam attempts probing for active numbers. With no identifiable caller and the advice to avoid callbacks, this fits a classic unsolicited harassment pattern. Block the number immediately to prevent future disturbances—telecom carriers usually offer easy tools for this. If it persists, report to authorities like New Zealand's Do Not Call register for investigation. Staying vigilant means treating unknowns as potential risks; verify any follow-ups through official channels only. Don't engage, as it can lead to more spam.
Caller is unknown, possibly spam. No message was left; they rang a few times then stopped. Do not call back.