Martin Lewis warned people with a credit card and asked them to check their bank statements.
The Money Saving Expert has asked people to make sure their details are correct or that some payments are being declined.
New anti-fraud rules mean that people who do not have the correct details with their bank can see that their details are being blocked and they cannot buy products.
The Financial Credit Authority told banks that they must verify a customer’s identity before allowing certain online transactions by September 14, 2021.
However, this has been postponed by six months to March 14, 2022.
However, the FCA said it would look into whether banks put the rules in place this month.
While shoppers must enter their PIN for payments over £ 25 when paying in-store, reports the sun.
Buyers are sent a verification code via SMS, phone call, email, generated card reader or banking app to confirm online that they really are.
However, if your contact details are incorrect and your card provider cannot reach you, your payment could be declined, warned MoneySavingExpert.
It has been reported that Santander is already verifying payments, while Barclays, Barclaycard and HSBC will be rolling out the changes starting this month.
MoneySavingExpert warned customers not to check that their bank has the correct phone number – for both cell phone and landline – and email address.
If you need to update your details, in most cases you can do so online or through your bank’s app – however some require a phone call.
One in three Brits is the victim of a fraud that resulted in millions of people sharing personal information that cost them financially.
A study of 2,000 adults through the secure messaging platform Letterbox found that 30% were deceived by a text message, email, or social media message pretending to be from a legitimate person or company.