Several of the UK's largest banks have been forced to stop offering customers foreign currency services as a result of the ransomware attack on Travelex.
Lloyds, Barclays and Royal Bank of Scotland, as well as supermarkets Tesco and Sainsbury's, have been hit by the problems at Travelex, from whom they get their foreign currency notes.
An RBS spokesperson tells the BBC: "We are currently unable to accept any travel money orders either online, in branch or by telephone due to issues with our travel-money supplier, Travelex."
On New Year's Eve, Travelex was forced to pull the plug on its websites in 30 countries after discovering a software virus infection.
Hackers, believed to be from the group known as Sodinokibi or REvil, are demanding a $6 million ransom in exchange for stolen customer data.
Travelex insists that there is no evidence that any data has been compromised but the hackers claim to have downloaded five gigabytes and are prepared to sell it within the next few days if the ransom is not paid.
Sodinokibi first appeared in April 2019 and have previously attacked 22 Texas municipalities and a host of dentist offices.
Travelex has not said whether it plans to pay the ransom but it is working with the National Crime Agency and the Metropolitan Police, which are carrying out criminal investigations.
In the meantime, the firm says customers can still visit stores, where it is providing services using pen and paper.
However, a backlash is growing over Travelex's response to the attack. Customers who ordered money online have been left "in limbo" as one told the BBC.
Meanwhile, employees have also been venting their frustration about a lack of communication from the company, with one anonymously telling the BBC: "We are as frustrated and upset as the customers are."