An new scam is conning people to divulge their bank pins under the premise of winning a grocery hamper.
The victims are people who have had their wallets or purses stolen a few days earlier and are asked to think of a four-digit number to receive a hamper full of groceries.
North Shore police Constable Damian Albert said because the callers weren't outright asking for a pin, it was easy to be tricked.
"A lot of people, if asked to think of a four-digit number, would give the same number they use as their pin, because it's easy to remember.
"It's possible that the offenders have used other business names with similar scenarios, and we'd like to hear from anyone who has had their cards recently stolen on the North Shore and has then experienced this type of phone call."
The scam was a reminder to the wider community never give out their pin, Mr Albert said.
Investigations were underway into two cases which had occurred recently on the North Shore.
In both cases the victim's belongings were stolen from their workplaces when they were distracted, including a reception desk and behind a shop counter.
Hours later the victim receives a fraudulent phone call from a woman claiming to be calling from Countdown supermarket and tells the victim that they have won a grocery hamper worth $500.
Police say the caller is very convincing and tells the victim that they need to provide a four-digit security number so that when they go to pick up the hamper from the supermarket they can be identified as the winner.
Police say they are following strong lines of enquiry, but warn that the offenders are very convincing.
Anyone with information is asked to contact North Shore police on 09 213 7811 or alternatively they can leave information anonymously through Crimestoppers on 0800 555 111.
