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Brian McKay, of Dunedin, said he went to pay for his groceries at Countdown Andersons Bay with his debit card on Thursday and the checkout operator told him a card had already paid for it using payWave technology.
The debit card he intended to use had no payWave capabilities but the bill was settled by his Visa payWave credit card, which was inside his wallet and in his other hand.
About two weeks earlier, at BP in Andersons Bay Rd, he went to pay for nearly $80 of petrol with his debit card but the bill was settled by his Visa, which was in his wallet and in his pocket.
Both times, he had the cashier reverse the payments and moved his wallet away to pay with his debit card.
He contacted Visa and asked for the payWave feature to be disabled and was told it was not possible.
Mr McKay wanted Visa to add a verification stage to the payWave process so unintended transactions were impossible.
He said he asked the checkout operator at Countdown Andersons Bay if unintended payWave payments were common and she replied ''all the time''.
''I think we need to be worried,'' Mr McKay said.
A Visa spokeswoman said Visa payWave cards only worked when the card was within 4cm of the card reader but Visa would investigate the incident.
Visa payWave cards were as secure as traditional chip cards and met the same standards for security.
''Since contactless payments were introduced, there has been no increase in card fraud,'' she said.
The Visa payWave cards were backed by Visa's zero liability policy, which protected Visa cardholders from unauthorised purchases.
''We recommend cardholders check their statements regularly and report any unauthorised activity to their bank immediately.''
The Visa website says Visa payWave uses a computer chip embedded in the card to send payment information to a reader at the point of sale.