What action should be taken when unauthorized transactions are detected?

When unauthorized transactions are detected, the immediate and most critical action to take is to report them to the bank. This step is essential because financial institutions have protocols and resources in place to investigate and resolve fraudulent activities. By promptly notifying the bank, it allows them to assess the situation, possibly freeze the account to prevent further unauthorized transactions, and begin the process of refunding any lost funds.

Additionally, acting quickly can help mitigate potential risks of further fraud or identity theft. The bank can also provide guidance on further protective measures to safeguard the account holder's financial information and identity. Waiting for the next billing cycle or discussing the issue with family does not address the immediate threat posed by the unauthorized transactions, and posting about it online could expose personal information or lead to further complications. Therefore, promptly reporting the unauthorized transactions to the bank is the appropriate and safest response.