A "technical issue" has allowed some customers with Papua New Guinea's largest bank to overdraw money from their accounts, while others have watched their bank balances drop.
In a statement posted to Facebook, Bank South Pacific (BSP) said it was working to resolve the glitch, which arose during the implementation of a new banking system over the Easter weekend.
"BSP would like to advise customers that due to a technical error some customers' balances are displayed incorrectly," the statement said.
The bank said customers that had overdrawn their accounts would have to repay the bank.
"Any new banking system implementation is a complex undertaking. Even with extensive planning, it is not uncommon for such projects to encounter technical issues during implementation," it said.
"BSP did not deduct or deposit any funds to any accounts and BSP is currently addressing the technical issue."
BSP declined to say how much money customers' had overdrawn as a result of the glitch.
"All our customer updates are published on the BSP official website and social media pages at this time," the bank said in a statement to the ABC.
PNG resident Rosemary said she overdrew her account by making a 600 kina ($257) online purchase on Friday, not knowing the funds had been incorrectly allocated to her BSP account.
Worried about online harassment of people who overdrew from their BSP accounts, Rosemary only wanted her first name published.
"It is a concern. If the technical issue did not happen, then I wouldn't [have made the purchase]," she said.
Rosemary said she could not get a refund on the items she purchased, but still intended to pay back the overdrawn money.
However she said she was considering switching banks after the debacle.
"I'm not going be blamed for that alone, because it's their issue. They should have tested the [upgrading] system, somehow, before it is applied to everyone," Rosemary said.
She also said BSP should have suspended all banking services when it became aware of the problem, to prevent people from overdrawing their accounts.
The glitch has also angered customers who were unable to access internet and mobile banking over the long weekend.
Port Moresby resident Joyce Morip said it was putting pressure on families.
"Just this morning … I went down to the shop to get breakfast for my children and now I can't do that because the system is still upgrading," she told ABC.
"It's very frustrating because it's the long weekend and you know, some of us have children to provide for."
Ms Morip said she couldn't check her account balance due to the internet banking outage.
Although ATMs are still working, she said lines were incredibly long.
"I'm not looking forward to standing there for hours just to know what's going on with my account," she said.
Wewak resident Arthur Awingi said 107 kina had disappeared from his displayed balance over the weekend.
"With that balance being minus, I was a bit worried but then the bank issued some statement that they will fix it very soon," he said.
"They will repay what is being taken out and your balance will be back to the original balance."
BSP is Papua New Guinea's largest bank, with about 2.5 million retail customers in the country.
Other customers have threatened to switch banks, complaining about high fees on top of the technical issues.
Goroka business owner Parks Ike said he wasn't happy with BSP's service.
"BSP are becoming a bit unreliable. At the same time they seem to be charging all sorts of unnecessary fees," he said.
