Criminals may find other ways to get the information they want, without the customer knowing; they can do this through social media platforms and other websites they've accessed. With this in mind, ask your customers to check their online banking account on a regular basis.
You can have them check that their account balance looks correct, look for any transactions they don’t recognize and ask that they report any irregularities, perhaps on a dedicated hotline or webpage. Consider providing information on how to spot a fake version of your website, such as by checking that the URL is correct and asking them not to enter any sensitive data on a page that look suspicious.
As a bank or credit union, you can help by monitoring for irregular activity on your end, such as checking the location of transactions, or flagging larger than usual withdrawals and transfers. You can also consider applying stricter conditions for when a customer needs to verify that a transaction is genuine.