The country’s biggest bank has made a $19,000 settlement offer to an elderly woman who was tricked into buying nearly $40,000 in pre-paid gaming cards from a Mobil service station by scammers posing as ANZ fraud prevention staff.

In a letter to the victim’s family, ANZ concedes that a fraudster posing as the woman phoned the bank’s contact centre and convinced staff to divulge personal customer information. This enabled money to be transferred between her accounts, contributing to the financial loss.

The bank also accepts it failed to record the woman’s son as having power of attorney over her financial affairs and says a delay in responding to the family’s complaint compounded her stress.

The settlement offer was “a token of our sincere regret for the way ANZ has handled aspects of your complaint and the time taken to resolve the matter”.

However, the woman’s son said the family believe the bank should compensate his mother for the entirety of her losses, given ANZ’s fraud prevention measures failed to notice anything suspicious about an 82-year-old pensioner making 13 separate “Neosurf” card purchases at Whangārei’s Mobil Plaza in the space of just 12 days.

“We appreciate that you acknowledge the stress this has put our whānau under,” the son said in a letter to ANZ last month.

“We ask that you reconsider your $19,000 offer of reimbursement and compensation. We feel that ANZ has underestimated both the level of responsibility and the raruraru [trouble] caused as a result of this fraud.”

But ANZ, which made $2.3 billion profit last year, has refused to budge. It said it was not liable for the entire loss because the transactions were carried out by the authorised account holder using a secure PIN, meaning they weren’t flagged as suspicious by ANZ’s security systems.

While ANZ was sorry the scammers were able to fool the bank’s contact centre staff into handing over the woman’s customer number and transferring funds, “the staff member involved believed they were dealing with an authentic request from a genuine customer”.

“ANZ would never intentionally provide this information to someone we didn’t believe was authorised to access your account.”

The bank said customers were increasingly being targeted by scams and it hoped this case would raise awareness and prevent others falling victim.

“We also appreciate you bringing this to our attention to help us understand whether we can make improvements to our own internal processes.”

The woman was targeted late last year and told she needed to buy the gaming vouchers to safeguard her money, before handing over card serial numbers to the criminals to cash in.

Whangārei police Sergeant Andrew Ivey said the victim was an “unwitting participant” in money laundering and it was highly unlikely the culprits would be identified or the money recovered.

In his opinion, the case raised serious questions about ANZ’s fraud detection measures, and whether Mobil had inadvertently helped facilitate criminal offending.

The son has also criticised Mobil for allowing the “highly irregular” transactions to proceed “without arousing suspicion or meaningful action by your staff”.

In a January 25 letter to the petroleum giant, the son said his mother struggled with technology and cared for her husband who suffered from dementia.

“[I believe] an elderly lady, who is very easily confused, spending such enormous amounts of money [should have] set off ‘red flags’ and prompt action.”

Twice, his mother made several large Neosurf purchases at the store in the space of a few hours.

“How did this not prompt Mobil to intervene?”

“You state that ‘Mobil is proud to be an active and engaged member of the communities in which we operate’. In our experience this could not be further from the truth.”

In response, Mobil’s retail sales manager Nathan Lee defended the company’s actions, said it was assisting police and assured the son that Mobil took such cases “very seriously”.

Lee said cashiers served hundreds of customers each hour. An internal review showed the victim was served by several different cashiers over multiple days.

“We will share the lessons learned from this issue with our network to help avoid any repetition in future. However, as you can appreciate, it can be challenging for cashiers to monitor or intervene in the spending habits of individual customers who are purchasing a legal product, especially when they may only be present for some of the transactions.”

The son told the Herald the family was disappointed with Mobil’s response and with ANZ’s position re compensation.

“In my view we were negotiating from a moral and ethical standpoint which doesn’t hold a lot of weight against a super power.”

ANZ declined to comment. Mobil did not respond.