Bank customers are facing further headache as NatWest further extends its trading hours to cope with the fallout from a computer failure almost a week ago.
Around 1,200 branches opened for the first time on a Sunday as staff battled to deal with a backlog of payments following Tuesday's IT glitch.
The debacle rolled into a seventh day on Monday after parent company RBS said it was still experiencing technical issues and confirmed some online services were unavailable.
The fiasco, which is also affecting RBS and Ulster Bank, has left many frustrated customers unable to access internet banking.
During the past week, people have seen payments to go awry, holiday and home purchases interrupted and wages appearing to go missing.
NatWest has more than 7.5 million personal banking customers, but it remains unclear how many have been affected.
More than 1,000 NatWest branches were opening their doors from 8am to 7pm on Monday as staff look to sort out the problems.
Susan Allen, of RBS Group, insisted that progress was being made and suggested customers would see their accounts largely "back to normal" at the start of the working week.
"The knock-on effects of this technical failure mean there will be bumps in the road," she said.
"We will do everything we can to minimise further disruption to our customers."
But customers have continued to voice frustration on the NatWest website.
Chris Latimer, from Liverpool, wrote: "wow first time since the glitch, i cant access online banking. this is not good."
Another posting, by Jean from Brighton, asked: "why can I not log into online banking to check my balance?"
Social media websites have been awash with criticism from people who found themselves without access to cash over the weekend or unable to pay bills.
Stephen Hester, chief executive of NatWest owner RBS , has issued a public apology over the matter and conceded the bank had let down its customers.
It came amid mounting fears that thousands of people could be hit with penalty charges if their regular payments - including mortgages - were affected.
The computer software problem has been blamed on an attempt to install a software update on RBS's payment processing system, which was then corrupted.
The group has said this issue has now been fixed.
It has promised that any overdraft fees or charges on current accounts incurred by customers would be automatically waived and has said it would work directly with credit agencies to ensure no-one's credit score was affected.