A savvy bank customer has trusted his instincts and recorded a potential scam taking place.

The anonymous Westpac customer was initially relieved his bank had alerted him to a fraudulent transaction. However, relief soon turned into suspicion.

"There was another transaction for $1230 so we wanted to verify if that was something you made as well?" the person on the other line said.

"No, that's not me. That's terrible," the customer replied.

The potential scammer said he would be declining the transactions, advising the customer not to give out his credit card information should he receive any suspicious texts.

As the call progresses, the customer's scepticism peaks.

"We need to confirm the digits after 8 before cancellation. After that, you'll receive a text message from us, and then that will be cancelled," the possible scammer said.

"You work at Westpac, right? You would have the data, won't you?" the customer replies.

The potential scammer is undeterred, replying, "The last 10 digits of the card today".

The customer then tells the person on the other line to cancel the card.

"Just cancel it, send me a new one. Then that's sorted, aye?

"I think you're not supposed to give out the numbers, aye?"

Westpac financial crime expert Jessica Channing said scammers are becoming more sophisticated as they attempt to gain their victim's trust.

"It really kind of struck me of like how believable this was when I first heard it," she said.

Nearly 2000 scams were reported to the National Cyber Security Centre in the last quarter – up 58% on the year prior.

Channing advised people who receive suspicious calls to "just hang up the phone and call us".

And it's not just calls – the Cyber Security Centre said the most common scam right now is phishing.

"It's really common to receive emails that are related to parcel deliveries or a Christmas deal," the Cyber Security Centre's Michael Jagusch said.

"I really do encourage people to just take that extra time. If you receive an email and it looks too good to be true, it might be and take that time to ask your friends or whānau if you're unsure."