Royal Bank of Scotland customers were locked out of their bank accounts and told to call a business rate phone line rather than the freephone alternative.
RBS, NatWest and Ulster Bank customers were unable to access their bank accounts online or through the banking app between 5am and 10.30am on Friday (21 September) morning, with the banking group reporting the failure was down to an issue when updating their firewall.
The company apologised but when customers took to social media to request guidance on how to navigate bill payments and money transfers, the company suggested customers call their telephone banking line on 0345 7888 444 - a number with local rate charges of up to 9p a minute from a landline and up to 55p a minute from mobiles.
But some customers shared their frustration that the bank had not offered the freephone alternative number, 0800 200 400, to those looking to make urgent payments.
One customer, Jo Williamson, said she regularly uses the freephone number and did not understand why the NatWest support team had failed to provide this to customers seeking help this morning.
Speaking on Friday (21 September), Ms Williamson said: "I use it regularly and it is working this morning, but is very busy.
"Not everyone has contract phones and inclusive minutes and I do feel that not providing this number was a little obstructive this morning."
When approached by FTAdviser regarding the chargeable number provided, a RBS spokesperson said NatWest switched to the 0345 number at a time when calls to a 0800 number were not free of charge for all mobile phone users.
The spokesman claimed RBS did not profit as a result of recommending the 0345 number.
Another NatWest customer, based in the south west, was unable to access a high-street branch on Friday (21 September) morning and tweeted her concern that she was unable to transfer money into an overdrawn account as a result of the online banking glitch.
Speaking with the FTAdviser, she said: "I am very much hoping that common sense will prevail and I will not be penalised - I understand issues happen, that is fine as long as the bank takes responsibility for any related repercussions."
All systems affected by the IT issues are now reported to be operating as normal and the banking group confirmed no customer data was compromised during the outage.